I think you're pretty close! Just put a bit more work into the torso shape and try to put more thought into consistancy in the design, like so:
What I did here was pretty minor, I just expanded the back by a pixel to give him a more natural spinal curve and made the shoulders poofy like the legs to give the design a better visual balance. There were minor things, like making sure the feet were always on the floor (you had a good bounce going already as it turns out, though I wound up adding top frames at the height of each stride to give him more ups) and using his belt to imply turning in the torso!
Edit: Most importantly, I also gave him a proper ass.
Also, post at original resolution, we have a plugin on the website that makes it so images posted here can be magnified without loss!