That's a pretty cool pose with a nice slight upshot. Good anatomy, too, but what's he doing with that left hand? Looks like he's about to spank himself.
Great pose - very dynamic over the shoulder. I think his head land neck look a little big, but I really dig his natural looking stance.
There's a real dynamism to the pose - I think when you add in the fingers on that back hand it'll be more obvious it's further back in the field than his butt and all will be well...
I like the shot, but the guy has a big head for my tastes. Proportional size is a personal preference though. You need to angle and foreshorten the left hand better, or draw some fingers in. Personally I don't think its a dynamic pose, but more a moody shot. Some good rendering could set it off.
His head seems a little large in proportion to his body. Try reducing it down about 10 % and the figure will look more in proportion, and a little more heroic to boot.
His right arm seems a little on the stubby side. You should perhaps lengthen the areas of his shoulder, his tricep/bicep, and his forearm a little more. A minor size reduction (5% or so) of his right hand might also help matters.
Other than the proportions, it's looking good.