Look at Fringe trees; Chionanthus retusus or C. virginicus.
Dogwood; Cornus florida or C. kousa.
Loquat is nice; Eriobotrya japonica.
My favorite is the Star Magnolia; Magnolia stellata.
If you can find a Prunus mume it would bloom during winter. Of course, since I live in Savannah, if you had this tree I would arrive in the dead of night with a shovel and steal it. The blossoms smell heavenly.