It gives off the impression that you just repeated the same shapes over and over and over again.
The basic shapes leaves the composition looking plain and the straight white background is helping either, shades of the same color in the correct areas would help in adding depth.
The mapping on the eye is messed up? You should make it taller if you want a more roundish shape.
Love the concept though, and the simplicity look just add a little here and there and you've got it.