Any plants must match your house and the yard.Between trees and shrubs and flowers should make nice combinations.colours need to coordinate. Sometime you need to deal with drainage/irrigation problem.
A pic is thousands words.I suggest you post some pics that show the context and situated and conditions(if have,include drainage irrigation)and the property
and the perimeter line.(They are not too close up.
a panoramic shot is good).
first upload photo to any photo-hosting site.Photobucket and Flickr are examples . While at that photo on the site,
look for a link to "share." Then look for a way of obtaining "html code" (don't select the thumbnail version.)
Copy that code and paste it directly into your message here.

In full sun, sure. For spirea--depends on what you want and the type. I really, really like a mixture of evergreen and deciduous, and I like differences in foliage color as well as the shape of the shrub.

Here is a picture. The back of my house faces west. To the left are the two dead trees which is the back of my property line. The 3 shrubs/trees in the middle are just beyond my property line. To the right is an electrical box hidden by bushes, someday I would like a garden there. For now I'm focused on those dead trees to the left which are being removed today.

{{gwi:29683}}

You should add a fire pic,a patio,a step sidewalk.
{{gwi:29684}}

Yes we would love a fire pit! So great to see the possibilities.

It's a bit confusing as what to suggest. Usually, if a person wants to replace a shade tree, they obtain one with the desired characteristics and place it at the desired location. You're inquiring about replacing two shade trees with a choice of plants that include shrubs and perennials so I don't know what to make of that. With the mention of "wanting a garden someday" back there makes me think that what you needs is to create a master plan that specifies what goes where and let it be your guide throughout the years.

If you're just looking for suggestions for a tree replacement, instead of tossing out the ideas of shrubs and perennials and very specific other small trees (that you are already set on)... maybe it would be better to describe the character of the tree(s) you are wanting to replace... if you are wanting suggestions for other trees. And, if you are already set on something, what is there for anyone to do other than tell you to "have at it and enjoy your choice"...? I'm confused.

We just purchased the house and the trees were already dead so we knew they had to go right away. I am not set on replacing them with trees and am open to other ideas. I like the idea of more variety back there.

If you want variety just start plopping whatever plants appeal to you anywhere you want to put them, allowing space for each element. If you want parts of your yard to have more meaning, you need to develop a plan...a scheme at least, that is based on objectives that you are trying to accomplish. Think about what those might be... screening, enhance view, privacy, shade, sun, less grass, more grass, lower maintenance, recreational use, utility, etc. A landscape plan does not usually pop out of thin air. :-) People can help you work out landscape issues based on objectives you've established. But there's not much anyone can help you with when it comes to whimsically plopping plants around the yard.

Agree generally with the advice that before buying plants to replace the dead trees you engage in some bigger picture thinking and planning. Being in a hurry to plant something that won't, in the end, fit with a broader scheme for the property wastes time and money. However, as a plantswoman, I would also be cautious about replacing dead woody plants with other woody plants without spending some time figuring out why the previous woody plants died. So, what are those trees and why did they die? It's hard to tell from the photo, but they dont' look like big old shade trees to me -- they look more like middle-aged cherry trees, or maybe birch? there are any number of reasons why they might have croaked -- and some of those reasons might make any replacements you're contemplating more or less appropriate.

I'm not sure what type of tree or why they died. They had pine cones if that helps. Here are some objectives I have, create some privacy, husband wants a fire pit, a play set for the kids, the back left I am leaning toward large shrubs. Back right I would like a garden where I can experiment.

Since you do have objectives, then you might consider that it would be a good thing to transfer those objectives into goals... specific things you can do to make improvements in your yard: put a certain kind of maple here... put a daisy there. That sort of thing. Let's call it a "landscape plan." You can make one yourself. Or consult with someone locally who will do it for a fee. It's too big of a job so someone here can't do it for you, but people here can guide you through the process. You don't need to do the whole yard if that falls outside of your area of interest, but you could break it down to half or just a specific area. If you don't really want to commit plans to paper, then maybe just talk about a specific project (like the tree replacement) and provide good photographs and try to solicit suggestions based on them. It seems that might be what you're trying to do here, but you need better photographs and information. The dead trees are barely visible here. We can't tell where your yard is. There's little frame of reference to your point of view (where in the yard you are and how this affects you.) Privacy is a great goal, but it would be really helpful to see what you need privacy from. There is a need for more information about the context relative to the objectives. Are the trees what you're trying to use to get privacy? (tip: any photographs you post make them large enough to see what needs being seen and of the scope enough to clarify the situation.)

>If you want variety just start plopping whatever plants appeal to you anywhere you want to put them, allowing space for each element. If you want parts of your yard to have more meaning, you need to develop a plan...a scheme at least, that is based on objectives that you are trying to accomplish.

You can also do something in between. :-)

YES, you mush have a plan, but it does not be detailed. You can even raid the clearance shelves for individual plants as long as you know what big picture goal you have.

What I am guessing is that right now, you want a screen about 6-12' high of mixed shrubs. You want to define the back of your property and add privacy and a frame for future design plans.

If that's right, then you don't have to have a full plan for the entire back yard at the moment, though I would suggest that you at least make a rough sketch and circle each area and give it a definition--future woodland garden, or future patio, or future outdoor kitchen, or future dining area, or lawn space (negative space is important too!), or whatever. Then you can see your mixed shrub border in context.

You seem to be focused on bloom. I would suggest that you think of bloom as a bonus and instead focus on the shapes of the plants, the texture of the foliage, and the color of the foliage, and whether or not it's evergreen (for screens, I like to continue to suggest a screen year-round with well-spaced shrubs). As far as blooms go, it's actually hard to create something unpleasant with a mixed shrub border, while it's really easy to create an eyesore that just looks like a big mess if you don't pay attention to shape, texture, and foliage color.

I have a 35'-ish mixed shrub bed that has at minimum one shrub in bloom, averaging 2-4, from April through October. But let me assure you, that's not what you notice! What people see first is the shapes and colors of the foliage.

I was new to the area, completely unfamiliar with the plants of this region, and living in a neighborhood that's positively infested with deer. For all those reasons, I could not see fit to invest a lot of money in shrubs that, for all I knew, would be eaten to the ground the first winter. So I bough clearance shrubs only. My altheas were my most expensive purchases, but I was comfortable with them from childhood--they were $15 marked down from $50. The rest were $1-5. I didn't know what colors many things would bloom. I didn't know when they would really bloom once in the ground. I just knew what shape they were, the color of the foliage, its evergreen status, and the projected height. And from that, I started planting.

I would do some things differently now, and there's a corner that got wiped out by the snowplow (before I marked the corners), but overall, I'm surprised with how well it all turned out.

Reyesuela thank you! Yes my main concern right now is a mixed shrub screen. Yours sounds beautiful! Any suggestions for zone 5? I also like blue spruce but those get way big.

What's your wind like there? I lived in 6a, but it was high desert, and the wind just dessicated everything in winter...

Color "rule": At least 1/3 of the foliage should be green. You can go crazy with purple, maroon, orange, golden, and blue foliage, but it needs a true green to set it off and make it look striking.

Evergreens: Evergreen "rule"--for a screen, make 1/3 or more of the shrubs evergreen.

If you don't have drying winds, there are a number of arbs that are green, golden, and silvery. Some make a more rounded shape.

Hollies can make a nice contrast to the fine foliage of the conifers. Many are hardy to your zone.

Many juniper/cedar will survive even the harshest winter. I don't like a solid block of the most common shrub juniper, but I've found the strong horizontal lines nice with other things. There are blue, chatruese-tinged, and green varieties. There are strongly vertical as well as mounding and vertical varieties.

Barberry comes in chartreuse and red.

Boxwood is hardy there.

Yew has a great super-dark green color, and the bright green of new foliage is as awesome as flowers.

If scotch broom isn't a thug there, it has an amazing texture, and its flowers are stunning.

There are some true dwarf spruces that have mounding forms. You don't have to get a gumdrop. I love Hoopsi! It's good for the back of a border, as it does get big.

Rodies and azaleas: There are evergreen varieties of both that do in zone 5.

Euonymus: There are a number of striking varieties.

Chamaecyparis pisifera: Some are overused, but in a mixed shrub border, they can be amazing. Boulevard in back, mops up front....

Lugustrum: The lowly privet! While it's terribly overused, its natural form (which you pretty much never see) is lovely, and it's a rare evergreen with large leaves.

Deciduous:

I'm not checking these for hardiness, so you need to!

Japanese maple--a few are hardy to zone 5, I believe.

Burning bush.

Smoke tree.

Sand cherry.

Nandina.

Lilac.

Mock orange.

Spirea--short-lived, fast growing, very graceful form. There are TONS of varieties with different leaf colors, sizes, blooms, etc. Get some with chartreuse foliage.

Annabelle hydrangea (arborscens).

Oakleaf hydrangea?

Roses. There are several roses that are disease-free and hardy to zone 5. Many roses are hideously ugly shrubs, but in a mixed border, their shape is lost under the gorgeous blooms.

Butterfly bush?

Possibly some laurels?

Red twig dogwood, particularly variegated. The're gorgeous year-round--put near the front.

Viburnums. I'm putting these last not because they're unimportant but because they are so incredibly gorgeous and under-appreciated. There are so many to choose from, with so many forms and bloom types! Their leaves are all green, but they're about shape more than anything else.

Organize for contrast and harmony. Fill in holes with annuals and perennials until the shrubs come all the way in. Some won't grow as fast as you hope. Others will get big faster than you expect. Don't be afraid to move them for a better appearance later.

Also, plant the shrubs closer than the spacing on their tags, or they won't grow one into the next but will stand upright like individual specimens in a sea of mulch! Take off 1/4 to 1/3 of the spacing distance. (I'm paranoid about overcrowding, so I do 1/4.)

You've gotten a lot of good suggestions, but definitely double check somewhere like the shrub forum before falling in love with something. A lot of those plants have serious issues in certain parts of the country, and we don't know whether or not you are, or are not, in one of those parts. Along that same line, if you are interested in planting conifers there, you really do need to get an ID and a diagnosis for those dead trees so the same thing doesn't happen to the new ones.

The plants I listed have all done great at ONE of my houses in my life, but almost all would not do at ALL of them! And some are invasive in some parts of the country but not in others. So yes, do check locally. :-) I've never lived in Zone 5.

I've gotten a bit jaded about having a perfect plan on paper. There are variables that don't seem to be caught by any paper plan--variables that only become apparent in a few years. Who knew that this "deer resistant shrub" isn't at all deer resistant in your neighborhood? Who could guess that your camellia will really, really really like your particular corner and gets quite huge 10 years down the road? So having a "big idea" on paper and giving yourself room to breathe with the details--room to change things, etc.--is really important for the homeowner/DIY designer. Also, be content with the thought that you'll be removing shrubs at some point, especially when the conifers get bigger. And sometimes, the conifers themselves will become unattractive--the boulevard Chamaecyparis that I love so much is pretty fugly in middle age.