Do a search on the internert for photo, women head, print it off in black and white so you can get a feel for the light dark and shaddows, shape etc. Reduce and enlarge to meet your needs( do be mindful of copy right issues) . Fisrt create the outine or shape , add pieces of fabric over the top using the photo/copy as a guide underneath. Use thread painting for the final detail and dimension.
I had a similiar issue trying to do hands... I found a site that had hands in all different postions.