Personally I think I'd go a lot smaller if I wanted to do only a two-frame run animation. That one you've got going on now is really not working, I'm afraid. I'm not sure it's possible at that angle. I'd go with four frames. You can probably reuse a standing frame in between steps.
This tutorial covers two-frame run animations well, and explains things much better than I can!
I don't have any specific crits. Everything is quite rough. I'm interested to see where it's going, though~