Your concepts in any drawing blew me away - the way you design them via characters. They're truly creative down to details and I hope to see more of that in your upcoming sketches.
I'm sure you're aware of this but it seems that your least strength is anatomy and once when you perfect at drawing the anatomy, your drawings will be incredible.
So how to work on anatomy? As for anatomy, postures, and forms, may I suggest http://posemaniacs.com? You can draw gestures of every pose at a specific time. It will help you to understand the structure of anatomy and how that understanding can flow into the form to make your characters come alive.
Just draw, draw and draw poses. Keep it up! =}