Your shadows are totally unnatural in every aspect. You have atleast two, actually perhaps three, global lightsources and the shadows from the bushes near the house make no sense in contrast to the shadows of the house!
the outline on the hedges looks odd, a little too light, maybe a darker green would look better? (still a light green, but a deeper one :P )
even if there are some mistakes in it i really like the stuff on the roof (even if i can't zoom in to see it better because of my stupid pc)