The lightness of the colored outline should follow the lightsource for best effect. Also, it shouldn't be much darker than the color that it outlines (enough to notice but not too much).
You should try to smoothen the more angular outline areas, through anti-aliasing or removal of outline (the vaunted selout).
I think your actual colors need more contrast, the texture doesn't read too well, and it needs a clearer defined form, the form doesnt read well. Redo your shading on the body. Make sure every detail reads well at 1x zoom.