the freehand on the disk is awesome and i like teh skull, too (maybe darkening a little che cuts on it). on the other hand, i thing that u could improve the sun on the disk (a little shading/highlightning) and the gold on the pack and arms. the armour is good but a little flat IMHO, maybe u could put a little freehand even on it or stronger higlights..
overall. very good job!