some possibilities:
aim the camera a little more to the right (not enough detail on the left (grey building)
put some bump material on the yellow stuff
create some more simple constructual details on the hanging roof like a small border
use a little more yellow in the sunlight and put one light beneath the scene that doesn't cast shadows >> you'll get less contrast in the shadows if possible use soft shadows
use photoshop to plant the tree (make a picture of your own tree and paste it in the picture)
put some real material on the gray stuff and a little bit of reflection on the glass
adapt the strange shadows on the shrubs on the left side by photoshop
good luck, i am lucking forward of seeing the result!!!