I was thinking, I don't know if I want to use any substrate at all anymore (so I can use my turkey baster to clean the bottom easier) but I thought maybe I could put fabric or cheap velvety fabric under the tank .. . maybe it would look cool or give a nice color to the bottom without being messy gravel or sand.
I have used wrapping paper, garbage bags, pillowcases .. . all these things taped to the back of my tanks for backgrounds. You might laugh but I had a blue sky Snuggie (for a Snuggie Pub Crawl) that I cut up and taped to the back of my tank . . . so it looked like blue sky with white clouds behind my fish. So I say keep your eye out for beautiful wrapping paper or anything you like as a background.