character creation

First off, the design is good at it's core. He looks like some sort of supernatural ninja, and that's what I think he should be: Some creature from another dimension, trained in the mystic arts of stealth and asskicking, though still quite young, even in our world's terms. What I would like to see improved on him are merely details, besides his pose, of course. For a rough sketch-up, this one is fine, but for a decisive concept art, you'll need a dynamic pose. Details I would touch up are the "eyes" or rather his visor - give the holes either a shiny look or a mesh texture like that of insect eyes. Currently, it looks a bit as if there's just his hair behind the mask's eyeholes. Also, wipe the friendly smile off the mask, and make it either a demonic grin, or a neutral, horizontal slit. No mouth at all, possibly some vertical slits, would also work.

And finally, give him some accessories, more "ninja" gear and a weapon.

Hope that helped