Was this inspired by Star Wars, the new trilogy? I think I recall the droids using something similar to that six-legged robot.

The picture really suffers from the dithering. Try to add brighter lines instead of it, it would certainly improve the whole picture.

Pretty good, personally I'm glad to see an iso picture here (it's so rare here nowadays), but the building and the trees are annoying. And try to add shadows as A.B. said. 

dommage pour le C/C des arbres sinon parfais

Woah! Picture would benefit from using of shadows underneath objects and from fixing some symmetric issues on big robot, but other of that it is an impressive piece.