I very seldom ever use a skin texture "as is", especially on nude character renders. I use the various tools/filters in my graphics program to change hue/saturation/contrast, etc., to get the effect I want. A lot can be learned by taking a texture and run it through some experimental tweaking. On some textures I also use local small area touch ups such as sharpen, blend, and other detail work. Nearly every graphics/paint program has filters and tools to completely change the look of a texture...and I think this is the method a lot of people use to create "new" textures from exsisting ones.