It's not terribly necessary to create new ones from scratch. If you've ever sat and clicked "Randomize" for a minute, you'll see that there are millions of new ones right there, and they are outside the realm of the DTE list. In fact, I would suggest doing JUST THAT, anytime you run out of texturing ideas! But for realism' sake, always use at least one channel of image-based texturing. There are nuances and shadings which cannot be replicated by anything other than a photograph. Even if you just splice it in as a "Random" texture...