very nice! I think it's a great scene.
@Kadri: not necessarily *adding* to realism, but the overcast skies provide you with a lot of GI light from all directions, which adds to lighting up the shadows under trees and in between vegetation. That makes it relatively easy for us in creating a realistic scene, because (I think), we have to work now with a reduced high dynamic range - which our eyes are made to cope with, but computer screens are not.
In other words, with that overcast sky, nothing is really bright, and nothing is really dark either. All tones conveniently sit on some middle ground that is easy to work with.