His feet lift high enough--people don't usually lift their feet very high when walking.
The head only moves a pixel in height, you could get a smoother effect if you increased the distance that the head moved during the entire animation.
The movement of the ponytail is really random and exaggerated. The hand bounces around oddly, it should swing smoothly, like a pendulum.
The chest appears to be rotating quite a bit, but the outline of the shoulders isn't changing at all, which looks odd.
The pockets on his jeans move a bit too far back I think.
I think the strap on the backpack moves too far as well.
The first guy's feet don't match at all, one of them looks quite a bit bigger, the blond guy's feet are much better.
Your colors are a bit close together, a little more contrast might look nice.
