Hey, here's my two cents. In this edit, I focused on:
1) Defining a hair flow and shading accordingly
2) Casting the hair's shadow against the face (also makes the eyes more visible!), and shaded the other half of the face to show form.

I also sought to improve the colors:
1) Skin palettes are tricky - A "flesh" feel is often achieved through the perception of all of the skin shades together at once, so you have to be really careful in how you do your color ramps. I used a fairly saturated light orange for the high tone, a desaturated orange for the midtone, and a desaturated warm brown for the bottom most shade.


2) Just as black colored objects are rarely represented through pure black, making white objects pure white is something that should be done with caution. Using an off-white as the hair's midtone, I saved pure white for the highlight. To give the white a greater vibrancy, I tinted the shades to a bluish gray.

Using off-white as a base color also pulls the most contrast out from the rest of the shades. (in this case)