I really like the gesture and the "vibe" here, I think it has a nice sense of drama. Two things that jump out at me though are the head and mouth "cowl" seem pretty big for ole Swampy. I think making that a bit smaller might help the general profile. The other thing is that while I do like your use of darks, I think this really needs some highlights to make it really pop. Maybe create a new layer and experiment with some highlights so you can preserve the vibe, but give it more depth.