the problem i have with this is that all the elements look too superimposd but not in a stylised good way
if this is a rendering straight from SU (the building i mean) increase the dark on the shadows, the contrast doesnt balance with the background
Change the tree in the foreground (it looks very 2d) with a photomontage tree, this will carry the continuity with the other planting.
add shadows from the new planting onto the building, increase the transparency to show the building to effect
use some lighting on the building layer, especially on the left side where is doesnt quite marry up
add a shadow for the main building onto the road
if u keep the reflection of the building consider warping/skewing it to match up with the direction of the road.
Maybe duplicate the vegetation near the building to the grass in the foreground.
sorry if any of it is over critical, i dont mean to be but if u are using photoshop and are wonding how to do an of the mentioned tasks id be happy to post up comments.