I'll start with improvements that could be made art-wise. The characters have a completely different look to background, which doesn't quite gel. These are flat characters in a very 3D looking setting. The lighting is especially confused, the light-beam directly behind the characters doesn't look like the light source, it doesn't even impact on the characters at all. Maybe you could introduce a third colour to the cell shading.

The wolf's pose looks a little awkward, one of his legs disappears behind a rock which does nothing for the dynamics of the fight scene. You might want to add a little bit of motion blur to the boy, the figures are awfully static.

But overall, this is pretty well illustrated. I love the background, it's well painted and the rocks have a wonderful texture. There isn't much to pick at anatomically with the characters, they look very correct and it is quite a striking pose ( I picked it quickly out of 60 or so images whilst browsing). The boy;s expression is great and he looks pretty bloodied, poor guy. I also liked your description, the image goes well with the story. Good stuff