It's kinda surprising how little texture is required to defeat the eye's "smooth plastic detector.
I took a high resolution skin texture, tiled it a bunch to get the right scale, and then resized it down to match the other skins, and the result is definitely a step up from just a solid color. It's pretty easy to imagine just adjust for the desired tone and then layering on features like lips and nipples etc.
The original texture file: https://s-media-cache-ak0.pinimg.com/or ... 3edafc.jpg
The resulting "skin":
The resulting rendering: