It depends really on how much room you have, whether you want a deciduous or evergreen tree, do you want flowers and if so at what time of year, etc. Stewartias are really nice, and also have exfoliating bark. Styrax blooms much earlier with little fragrant bells. Serviceberries are lovely in spring and fall, and good for wildlife (people can eat the berries too). Be more specific and maybe we can narrow down the list!