I like it.
Minor crits:
A human skeleton has two bones in the shin and forearm.
The ankles don't bend at all. Is this intentional? It seems if the knees bend, there is no reason for the ankles not to.
The black outline is a little heavy, your 45 degree lines could be cleaned up a bit.
Where is the light coming from? The lighting on the near arm (the one with the sword) seems inconsistent with the lighting on the near leg.
I think the hips should move a little bit, with the walk, but I've seen other animators get away without it. Depends on how realistic you want it to be.
Are you looking to convey any particular mood with the walk? Should the skeleton be threatening, or scary? Or just a normal walk? If you want to exaggerate the scariness, I'd recommend making him hunched over and lurching a bit. for a normal walk, the upright is ok.
Oh, and here is a link to one of the masters of his craft animating some skeletons:
http://www.youtube.com/watch?v=5yYeZMx1Y7UHope this helps,
Tourist