The concept is nice. but the target shape in the lower left corner kinda kills flow. Also you should try adding some complementary colors. a little yellow/orange would go nice in this one.
Quoted for effect. I'd also suggest removing a good portion of those brush layers, instead make smaller brush strokes over him and make a depth effect. (in front and behind Master Chief). And oh... can I have the vector Master Chief please? :3
Good start to a new style. Might need some work since brushes are very visible and the colors need changing (C4E explained that well). Oh, and maybe stronger lighting is needed, no one seems to have mentioned that. Looks better then anything I could do in that style though so *thumbs up*
Hmm,I dont know,I dont like it,the render looks like its over contrasted,and its too simple,maybe adding some text would have made it look better.