All the anatomy seems correct. My only critiques that come to mind are that the whole picture needs a little more texture(especially that canvas bag),also the robot's "skin" needs more contrast to appear more metallic. Since metal is a highly reflective surface, you should have some really bright points and really dark points, and probably some kind of reflected light from it's surroundings.
You have some of that reflected light going on on the robot's right arm, but I think you need to push it a bit. Hopefully my advice can be helpful!