Some people are making this unecessarily complicated. Things that you find, you can use them in your work, use them for renders, it is in matters of redistribution that the problems arise. If you make something available to others, either for free or for sale, EITHER - it must be completely yours from the first pixel and the first vertex - OR - anything else in it, you must have permission from the originator. So in answer to Charlie Tuna - you can use that texture all you like in your own work, but you can't redistribute it as part of some project of your own (say a character package).