why is this so underrated???
AHHHHHH!!! lets see. a darker shadow under the neck... uh... when skin has creases, often it has a little shadow to make it stand out, and I guess I could add sometimes skin has a bit of pink on the cheeks, nose, chin and forehead, but that is up to you... (not a expert)
this looks good as is. sometimes a drawing doesn't need a whole bunch of color to look good! but if it bothers you, try adding some glossy lightings on the lips and nose, and eyes if you want^^ a bit light on the hair would also look good (I'm not a expert)
heeheehee