Picking a mood could really help you decide how you want to shade something, and helps with colors too. Other than that, I suggest doing some block shading to get a general idea of shapes and light source, then you can worry about things like shading styles and how to make something look more like hair. Also, the white background is detracting from what you have. Picking a color would not only help us see the piece for what it is, but help you do the same while you work on it.