The arm, man, the arm. It's just lying there stiff, flat! The whole composition is pretty boring, to be honest, because if he had just shot a gun, he'd be recoiling back, not standing there looking bored as you have him. I'm not going to tell you to redo the pose, because you've done a good amount of work, but rethink the position of the arm.
I also think the scarf is a little unnatural, but that might just be me. Oh, and I proffered the darker, more steam-punk-ish colors, but that's a personal preference.
I do however like the pants and how you shaded them, and the gun is done very well. You've basically got the pixeling down, now just work on the pose.
Keep it up! -Dex
