tricks for shadows
if you painted this with photoshop here is a trick that could fit well in this pic, since the character is lightened from behind you may want to paint the whole character with a big highlight on the edges and dark shades on the center of the body,
like make a copy of the whole character layer, then ctrl-u adjust the brightness to -50% or so, then use a mask to erase the edges and some strategic areas, this will create a nice cell shading effect that will add realism to the pic and create stunning effects.