compo is off, and the lighting is strange, try not to put an random arbitrary brush as the primary lighting element.
How is a 175px soft-edge round brush random? And how is it arbitrary if that's where the light source is coming from?
it looks good but he is right about the light source maybe if you darkened around the edges or something to make it seem like the light is doing more to make it a focal point or something.. overall good sig just needs a bit more work