his arms are too thin, make his white shirt material go more onto his pants on the belt level. use selective outlines, which is to me, using one tone darker color(from the perspective of the color you make an outline on) for the outlines.
Also, his torso seems kind of "blocky", like a rectangle. I presume that you wanted to use this kind of style, but i think that SOME anatomy basics are crucial for all kinds of styles.
