Yeah, it is a bit tricky. I'd say just keep searching for the right texture on what you want to apply it to. Also, you can always modify it, erasing, painting on top of it, and combining it with other photos.
Actually I don't go on CGTextures...Although I should probably start, haha. I just use Google and make sure to manipulate he image so much, it becomes difficult to see the original.
But this is an older image, when I was just trying this method out for the first time. I'm going to upload a couple recent images, where I use textures with more painting on top to get what I want in the 1st place.