Well, first of all I like some things about tehwexx's edit, but you're past the design stage and are working on giving the character a full set of frames now, so you can't realistically implement much of his edit, expect his palette maybe, which I kinda like.
---Oh yeah, his foot doesn't touch the ground at all, when pushing it gets level with that white line on the board, the side of it. Didn't notice that before. Hehe, this reminds me of
Marty from Back to the Future. Take off those wheels, add some random bobbing floatiness and yer in business! Ok . . . no don't do that.
I always liked the exaggerated proportions of the dude with respect to his skateboard but now it looks like it's a detriment, unless you get really creative maybe. What I'm acknowledging is that the skatebaord is obviously over-sized; it's almost as long as he is tall.
How does a small child properly sit in a chair too large and still plant his feet on the ground? The obvious adjustment fix is make his foot come down all the way to the ground, which I'm guessin' would be 1 pixel below the wheels' bottom pixels. That'll leave him needing to have elastic legs or bending down more to get his foot all that way when pushing off. And it's important to get that foot flat on the ground, so no tippy-toeing.
Unless his hoody is connected to his belt in the back, how is it not catching wind and flailing out more than it is? Try adding a little dramatic rippling to it. This may require adding frames.
Speed lines?