That's a tough one, but mostly because you haven't told us much of the place or the yard, other than its size.
I use the "Recommended Species" lists to make recommendations. The link is to the recommended species for Washington DC. These lists are sortable, so when I select "6-12" and "12-36" feet high, that still gives me a list of 43 possible trees or shrubs for your place.
I'm imagining you would want something in the 10-20 ft range and maybe some colorful aspect in the leaves or fruit to give it a seasonal highlight. My list follows, but you could select your own by sorting the recommended species and applying your own preferences:
Asimina triloba (Pawpaw)
Cercis canadensis (Eastern redbud)
Hydrangea arborescens (Wild hydrangea) would just fit nicely if you want a smaller shrub
Morella cerifera (Wax myrtle)
Sumac family: Rhus glabra (Smooth sumac), Rhus copallinum (Winged sumac), Rhus aromatica (Fragrant sumac)
Rhododendron family: Rhododendron prinophyllum (Early azalea), Rhododendron maximum (Great laurel), Rhododendron catawbiense (Catawba rosebay), Rhododendron calendulaceum (Flame azalea)
Rhus typhina (Staghorn sumac)
Sambucus nigra ssp. canadensis (Common elderberry)
Viburnum rufidulum (Rusty blackhaw viburnum)
