I would like to see content creators include, as one of the previews for models, part of their skin texture. I can often get a good idea of how "realistic" the texture is from renders, but if I'm looking for a particular skin-tone, the lighting used can really throw me off. I've bought a number of textures which were very different under a neutral light than they seemed in the previews.

One thing I do with my texture/character packs is to do my promos with Poser neutral lights (1 white - 2 gray) so that the prospective buyer can get a good idea of what it looks like without fancy lights.  

If I include custom lights, I'll do one promo image using the light presets, again to give the buyer an idea of what's included and how they affect the textures.

if you are looking for a "particular skin-tone" , then as long as you keep it for your own personel use , there would be nothing wrong with you duplicating textures and adjusting thier tone in Photoshop or whatever app you have, if you do that just make a folder somewhere that has the creators name on it (so you don't forget) then you could store a multitude of different tones of the texture you like best in it.

and if you make a render with it and choose to credit the creator, then just mention that you tweaked it a bit.that way anyone that likes your piccy can know that that isn't how it looks as default.