mmmmm textures. I can't help it, I like me some (uh-hem) gritty, grungy backgrounds now and then. I think that's due in part by my roots as a scenic artist. Got a wall that needs paintin'? Let's throw some texture on that bad boy first. Anyway, I digress. The Texture King is a good resource for when you need a free, high res image. They've got over three hundred at this point, plus they're organized nicely so it's easy to find what you're looking for.