Think vertical. Can you do trees? Maybe something like Parrotia 'Vanessa'. If shrubs, maybe something like Physocarpus 'Diablo' that has canes and is vase-shaped.

I think the variegated foliage would be a nice contrast, same thing with Diablo with its purple foliage. (or new Physocarpus Summer Wine). Although with just morning sun, they may not reach their full potential on the color thing, but they will still be good.

Cornus 'Ivory Halo' is supposed to be not as big as common variety, but it can still get big and may have leafspot problems in wet years. Another variety 'Cream Cracker' is supposed to have more resistant foliage. Seven-sons tree - Heptaconium mac...(?) - is a small quick growing tree with great unusual bark.

Are you thinking 3 of the same thing? I think with the solid background, diversity in the next layer would probably be best.

Hmm. I had been thinking shorter, but I do see the point about the Ninebark. They had a few, and the burgundy color was gorgeous. The nursery had a lot of the variegated cornus (ivory halo)? The manager there said it has proven to be indestructible - they actually cut it back to the ground and it came right back.

If deers and rabbits are not not an issue, Wendy's suggestion of variegated Cornus alba, be it a full version or a dwarf(ish) Ivory Halo is perfect.
If you are more interested in flowers, such 'see thru' shrubs as Kerria (for early spring bloom) and/or Buddleia (for the late summer bloom) could be used pretty effectively.
As a matter of fact I'm working right now on a pretty much the same border/ seasonal screen and regretfully rejected Cornus alba idea because of the deers issue.

Hmm. Deer. I didn't know they eat Cornus. That could be an issue. They haven't touched all the native high bush blueberries, which is odd. I don't think there is much "pressure" on them because we live near a lot of woods and fields (this is still a pretty rural area). However, I don't want to open up a salad bar for them, either.

I thought Buddleia need pretty much full sun? Same issue with Spirea, correct?

I've never seen a rabbit. Woodchucks, yes. And they are plump little fellas.

I don't have deer so I couldn't recommend on that basis but site unseen, I might opt for a broadleaf evergreen like the meserve hollies - Blue Prince and Blue Princess.

Deers would normaly leave cornus alone in a summer, but may chew those bright red twigs in a winter. Rabbits definitely will.
Re: Buddleia/Spirea and sun.
If site has at least 4 hours of uninterrupted sun, both of them will bloom fine, though yellow leaved spireas will not be yellow, but rather lime green and fall color will be not that interesting.

I really like the suggestion of the Parrotia 'Vanessa' both for the vertical look and for the spectacular fall color. Your viburnums don't have much in the way of fall color. Another option for vertical would be a Magnolia 'Sunspire'--very vertical with yellow blooms, highly deer resistant and fully hardy in zone 5.

A contrasting dark backdrop is the direction to go in, really makes the flowers stand out. Something evergreen would provide structure.

How far apart are these plants going to be and how much depth are you giving them?

I think the Parrotia Vanessa get to big. From what I read, they will reach 8'. I really want something that will be smaller than the Viburnum. I am trying to go in decending height - the large trees behind, then the Viburnum, then shorter shrubs. There will then be some grass and and raised bed (then more grass, then the street). The raised bed will probably have a small tree, a few small evergreens and perennials.

According to the label, the viburnum will reach 10' wide, so I was going to space them about that far apart, maybe a little closer.

By depth, do you mean soil depth or spacing? Soil depth isn't an issue. I hadn't really thought about spacing depth. I guess they will probably be put about 5-8' from the edge of the treed area.

Sue, though the Parrotia and the Magnolia get tall, they stay very narrow, which I still think would provide very good contrast in form.

Smaller and vertical--how about Miscanthus 'Little Zebra'?

Thanks everyone. You have given me some great ideas. I'm adding all these plants to my wish list.

I hadn't thought about Miscanthus there, but it might be just the trick. I think I am having analysis paralysis. I am so afraid of making a mistake that I just can't make a decision.