His face is too dark and he doesn't pop enough from the background. Did you make that background or was it a stock? Either way, its freaking sweet!
Try painting some very light white brushing over his face and set it to overlay. Only his face though, make sure its not over the background at all. (Make a new layer, select the render by Control+clicking on the render layer, make a layer mask, then do your white brushing on that new layer). Hope that makes sense. I think that will make a ton of difference in the sig. Overall, its sweet though.