I laid out everything that I've gotten so far and have spots for 2 more things.

1. Full sun... from dawn till 3pm, fairly hot spot, near driveway and street. Needs dark foliage, but not something that may dislike periods with wet feet (sedum, for instance) since it's at the bottom of the bed and may stand in water after a rain. It's in the front of the bed, so 10" or less in height. I have Geranium Hocus Pocus nearby, so I don't want to use that again so close.

2. Part sun... early morning and a couple hours mid afternoon. Needs silver/blue foliage.

Remember, I'm zone 4.

What do you think?

Dark foliage:
Ajuga Dark Scallop
Heuchera - many dark foliaged, and since we are so far north, I don't think that this spot will have too much sun. Probably want to create a low mound to plant it on so that the crown isn't actually under water.

Also consider Persian Shield for part-shade - the foliage is purple-ish with overlay of silver and blue, it's fantastic for foliage effect. Some sources say it can take full sun but I've always grown it in part-shade, so not sure about the full sun. You'll find it in the annuals section.

Re: Japanese painted fern. Gorgeous gorgeous gorgeous when grown well (read: moist, part-shade conditions) but I always buy ones that are silvery from the get-go. A lot of them are greener with just a hint of silver, and the one that I purchased like that has never gotten the silver coloration, even though it's a mature fern.

I've also found that shorter dark-foliaged plants needs something next to them/nearby to make them pop; otherwise, they tend to be unnoticeable, even in full sun.

Sandy

Would a see through type foliage plant work such as Husker's Red Penstemon?

I really like Firecracker Lysimachia & cut foilage back because I prefer the purple leaves & skip the yellow flowers. I put them in pots near our dove cages to greet me daily when I feed them. Still it will be taller & kind of floppy, so might not be the edger you want.

One way to keep ajuga in it's place is to sink a large pot of it & keep the runners clipped. When it's above the other plants those runners don't root.

Maybe try one of the brown Carex ornamental grasses there for a neat front of border plant. I had some further back last year, but pulled them forward this year and to a corner in some beds and I like it better. The longer tips types aren't my favorite unless in containers because the tips get caught up in other foliage. I've often been tempted to snip the tails.

Many of the annual in your zone red flowered snapdragons have dark foliage or possibly darker markings on tender perennial geraniums. Many have very lovely accents.