My personally feeling is its going to get to a point where you just can't tell. Since the posette, vicki and other figures have only one way to texture them and everyone is going to put on make up, shadow, hilight etc. in the same spots, it gets real fuzzy. That's kind of like copyrighting the paint scheme of your house based on white and grays. What I would recommend for texture makers is to seriously think about embedding codes in your textures. This isn't fool proof but, if hidden well enough they may get missed at first glance. For example, you could form your name in the complex browns of the skin or even add Digimarc to the texture. Its not a cure all but, if you can show you're little marker in a "stolen" texture, that can go a long ways to proving you're right. Basing a judgement of texture theft based on a render is incredibly inaccurate.