It's at a point now where it's on the line between complex robot and simple, stylized, somewhat cartoony robot. And I think it would look good going either way. Perhaps add some joints, a higher quality texture, and maybe some gears, lights, wiring, etc. to the chest and head if you feel like going the way of complex. Or maybe limit the number of disks at the point where the legs meet the pelvis (or just completely remove them), maybe exaggerate some features, and throw the bumpmap out if you want to go in the way of cartoony.
It's a promising WIP, and I like the composition and the simple backdrop with black frame. I look forward to seeing how it progresses .