PS: does it even look like a girl/woman??
It does have more of a feminine look than a masculine one.
First I suggest using a custom lighting for modeling,as you model and get further/satisfied with the looks,rotate the lights and jump in it again.This is specially useful when roughing ut the basic masses because it will show you what light planes are defined etc…
On the details side,stop right there,you’ve got enough so you can have hours of Tweakin’Fun.For now,try to concentrate on getting the skull correctly,this will drive most of the head’s shape(you’d be surprised how much the skull shapes shows through a head’s skin),then you can go on with other medium details like the eyes,mouth and nose using Magnet operations.
It’s good to refer to images but you’ll learn much more if you use them outside the viewport once the basic general shapes have been roughed out and so will it practice your measuring skills.