Cool pic! I really like the arm and leg structure in this. Although the hair looks like it could be a bit more fluid. Try to make it flow, almost like a liquid. Good hair tutotials can be found at http://www.polykarbon.com and http://www.jdillon.net . Also, I assmume you're coloring in Photoshop, and I notice you don't have many highlights, just shadows. Try to not only shade, but also add highlights to brighter areas. And the shading underneath the girl's breasts on the left seems to be a little splotchy. If you're using the Airbrush tool, try using the Paintbrush tool instead, and set it to 100% opacity, uncheck wet edges, and there ya go. Overall, a great pic, keep it up, I really like the coloring and character design. ^_^