Buddleia/butterfly bush grows 6-8 ft. tall and blooms late in the season, generally purple or lavender fragrant flower clusters. It blooms on new wood so needs to be pruned back to about 8" every spring. It will regrow to it's full height over the growing season. Dead-heading will extend the bloom for many weeks.

Weigela is a spring bloomer with pink or white flowers that grows to 5-6 ft. There are many dwarf varieties but mine is W. 'White Knight.' It's supposed to grow 5' tall but this year it grew a foot taller than I am.

Philadelphus/mock orange will grow to 8-10 ft. over time. Blooms in full sun in late spring. Rose of Sharon/Hibiscus syriacus can grow very tall; blooms late summer/early fall.

Where is the bed situated ? Full sun or shade? When is the back drop required to bloom? Any particular colours preferred? Tall perennials: Rudbeckia Herbstsonne, Eupatorium purpureum, Helianthus Lemon Queen, many Sanguisorbas , Heleniums, Aster novi-anliae, Aconitum Spark's variety, Aconitum carmichaelli. I have posted a lot of pictures of tall perennials in following threads:

August Jewelry, September Gems, October Delights and November Pleasures

Here is a link to the first of them:

Here is a link that might be useful: August Jewelry

Hydrangea paniculata 'Limelight'
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Hydrangea 'Preziosa'
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Echinacea varieties
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Mixed perennial border (tall perennials) - echinacea, phlox, russian sage, rudbeckia
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Some suggestions
- Polymorpha persicaria - takes at least 2-3 years to achieve size but well worth the wait. Flowers for 6-8 weeks.
- Physocarpus 'Summer Wine', 'Dart's Gold', 'Coppertina' - nice, but brief spring flowers, colorful foliage all season long. Can be pruned to keep size you want
- Eupatorium 'Gateway', mine get 5-6 feet but needs full sun & consistently moist soil.
- Miscanthus 'Morning Light'
- Sambucus 'Blace Lace'- needs consistently moist soil to look it's best.

I keep a tall (about 8 feet) hedge of Loropetalum formally clipped that serves as a backdrop for my front perennial border. Plants really pop against the dark foliage. The one drawback is it has to be sheared about every six weeks to look its best in summer. But, it is evergreen, blooms spring and fall, has interesting autumn leaf color, and is absolutely bulletproof. Plus, I have found that virtually every color works with dark purple.

Camellia has evergreen glossy leaves and large blooms. They take several years to reach mature height.
http://www.walterreeves.com/gardening-q-and-a/sasanqua-camellia-and-japanese-camellia-identification/

Camellia sasanqua grows to 6' - 10' and blooms fall through early winter. Partial to full sun.

Camellia japonica can be up to 15' depending on cultivar and blooms mid-winter through spring. Does not thrive in full sun.

Gardenia could be considered if you want something not quite as tall, with some cultivars 4' - 6'.
http://www.walterreeves.com/gardening-q-and-a/gardenia-varieties/

Both Camellia and Gardenia like our acid soil. Give them a little hollytone or ironite.

If you find someone with a bush that you like, both can be rooted from cuttings. I have some Gardenia cuttings in the process of rooting I have seeds and seedlings (open pollinated) from Gardenia jasminoides if you are interested in trade.

Here is a link that might be useful: UGA Downloadable Plant List Publications