I really love the way you draw attention to the robot's head. I know you've been working with zbrush lately, and I initially thought it was a 3d rendered image. The way you focus in on it while leaving the surrounding areas blurred really gives the image a sense of depth. Excellent work.
My only crit I suppose would be to tighten up some of the edges just a little bit, for instance, the band that goes around its waist. The width of the band is inconsistent--making that symmetrical is just an example of a tiny little touch up that I think would go a long way.