I think you might want to work on the line quality first and foremost (and by line, I'm also including boundaries between colors). Right now the lines are quite haphazard, and look quite rushed. They really need more love. Don't rush things, take your time. That is, after all, what pixelling is about. Forethought, and careful pixel placement. Your lines are uneven, with slopes and curves having differing steps. The anatomy still has issues, not just with proportions, but also with the shapes (his right elbow, for example, is this oddly-long curve, and the forearm is overly rounded).
Did a quick paintover showing some changes to the lines, to show you what I meant about line quality and evenness.
