He is about to fall - so it is quite dynamic character :---).
IMO it would be nice if there was more shading on the whole Sonic, or if his head wouldn't shine so bright. If you decide to use shading - use it on the whole character.
I think it needs a border, i can't see if there is one at the moment but it's very faint if there is.
Try darker shades of the the same colour rather than black though.