Edit Sim face bump map?

I have always wanted to make an anime type look for sims, but they have so many distinctive crevices and lines in their faces so that even using a custom skin isn't enough. I've made a skin I really like to use, but there are still shadows on the sims face that I just can't get over. Can anyone direct me to where I can even access this bump map? All that comes up when I select my skin (after selecting make a new mesh under CAS) and go in warehouse is just one line- the swatch for the skin.
Please help?