I can't think of many things that can be improved here, but here's one. The wings are suppose to be modeled after a bat, but they don't have the same shape. Think of the wings as an arm with long fingers and skin between them, like this- link and this- link. Right now I think the arm portion of these wings is too curved, so it doesn't really look like they have an elbow.

Other than that this looks very good. Maybe try to include the background color into the dragon's body in a few places as bright highlights. Right now I just see it in the horns, eyes, fangs, and wing thumbs while the rest of the body is just 3 colors.