The optical ilusiun was first it what came into my mind.

Looks like the rabbit/bird thingie to me.

Tnx i will fix. 

looks a lot like this classic optical illusion .... the beak is too far away from the head i think

 Needs some anti alias.

Tnx for the advice, I will improve it. 

Very good job! :)

I think it could be better by adding more light on the top of the bird's beak and head.

The clouds deserves to be shaded and if I were you, I'd erase the sun - it seems to a be a bit too cartoon-ish.

Though I like it! :)