Just for some examples, I have winterberry holly, red osier dogwood, red bud, arrowwood viburnum, cornus alternifolia (AMAZING mahogany red early spring new leaves), clethra summer sweet (I have white flowered one but there is a pink flowered variety that I want to get as well), blueberries (gorgeous autumn color).... Speaking of autumn color, be sure to consider sugar maple if you have the room.
For flowers, iris versicolor, wood poppy (recently finished blooming cheerful bright yellow), virginia bluebells, marsh mallows, liatris, coneflowers, asters, ... oh and trumpet honeysuckle (in full bloom and attracts hummingbirds and nesting birds in the vines).
Look for native plant sales in your area. If you are not too far, Bowman's Hill Wildflower Preserve in Pa (just north of Doylestown) will have a big one on Mother's Day weekend through the weekend after.