There is no texture, and hardly any shading. Pretty boring unless you like one color cubes with a sign on it. The door is horribly colored to match that red, and dos not really look like a door, more of a square crap colored thing on the front of your building. It looks like you made it in MSPain in less then 10 minutes. You can improve a lot on this.
How to improve:
1. Add texture to the walls
2. Add some shading other then the roof
3. Change shade of red to something darker
4. Redo the whole door and use some effort this time
5. Change the color of the door after step 4
6. Add something on the sign
If you follow these steps correctly the building might turn out good, depends on how much effort you put in to it. It should take some time to make a good piece of art.