Here is a handful of ideas you might choose from
Red Buckeye (Aesculus pavia) is a clump-forming small tree with dark green foliage and red flowers in spring. Loebner Magnolia (M. x loebneri) and Saucer Magnolia (M. x soulangiana) form broad, rounded canopies and have pastel fragrant blooms in early spring. Crabapples (Malus species) offer a pretty spring show and are tough and durable in heavy clay soils. Paperbark Maple (Acer griseum) has attractive brown peeling bark and an upright, oval-shaped canopy of pale green to blue-green leaves. Redbud (Cercis canadensis) blooms a tangy lavender-purple in mid spring and has clean, heart-shaped leaves. There's also a purple-foliage variety called Forest Pansy. Finally, for dappled shade, you might try Sunburst Honeylocust (Gleditsia triacanthos Sunburst). It leafs out golden yellow in spring and then turns green. It may grow a little behond the height you're looking for; it can get 35 feet tall.