Hi.....

I like Serviceberry trees, especially 'Autumn Brillance'....They would seem to fit in your space....They have beautiful flowers in spring, berries for the birds and you and bright red leaves in fall. There are two forms offered I think, tree form and a shrub form. I included a URL that might be helpful with info and some pictures.

Paul

Here is a link that might be useful: Autumn Brilliance

Purple plums tend to loose their leaves very early in the season and there is no fall color with them.
Styrax Obassa is small. There's Redbud Chinensis ALba, a white flowering dwarf redbud, several types of dogwoods, fringe trees (also called Grancy Greybeard), smoke trees which make fantastic small trees which flower unique puffs of "smoke" and often turn colors in fall - many cultivars have colored leaves.
I also agree that "Autumn Brillance" serviceberry would be a lovely choice.

GGG

I love my Vitex. It has blue flowers in the summer and attracts hummingbirds. It can be trained to look like a large bonsi and is a fast growing tree/shrub that is an herb with an unusual smell and shaped leaves. I also have a white flowering one and one that is prostrate and doesen't get over 2/3 feet high. frankie Lynn

The best idea I've read so far was the Crape Myrtle. Very nice when trimmed like a tree, flower color is selectable and is drought tolerant.

You could also try a Japanese Maple (different cultivars) or a Dogwood - but these get tired looking after July 4th.

There are many things you can use in that amount of space. Do you want it to grow tall and narrow? Evergreen? Flowering? Fall color? Fast growing? Slow growing? Native? Exotic? Sun conditions? Overhead lines? How close are the nearest buildings and plumbing lines?

Dogwoods do not have to get tired looking at all! You just need the right cultivar. Crepes can get very tired looking, many get mildew, are attacked by japanese beetles and frankly, so many streets are absolutely lined with them, they get very boring. Again, with crepe's you need to be careful of the cultivar you choose. One that has fall color and exfoliating foliage is a great idea. They do need more selective pruning than many other trees. To be able to garden well under them you need to make sure and keep the canopy open by selectively pruning cross branches. The interior can become a very tangled mess of cross branches.
Vitex is another very good choice. I have one, and it blooms twice a year.

GGG