Hi Donna,
There are many landscape trees that you can use near a door. I will assume that you get sun in this area and it is not all shade.
Flowering Dogwood - this tree has all season interest. It has lovely flowers in the spring, berries in the fall, pretty leaves in the summer and even an interest tree shape during the winter.
River Birch - more narrow, particularly towards the bottom. It is not dense and rather wispy, so you can see through it somewhat.
Star Magnolia - early blooming tree, one of the smaller trees.
Enkianthus - small tree/large shrub - beautiful bell like flowers. May be hard to find.
Crapemyrtle - comes in many sizes and flowers in the summer
These are just a few that you can use. Be sure to check out what the diameter of the tree will be at maturity, and place it appropriately. The larger the diameter, the further away from the door you must place it.