Try those slate tiles. They are VERY easy to clean. Just wipe off with chlorhexidine, and scrub with soapy water probably once a month. Since Leopards like to pick their potty spot, you could easily just place a piece of paper towel down and you wouldn't have to clean often at all, just that one spot.

I know I've seen some really nice looking tanks done with slate. The person made caves, ledges, bridges, ramps, steps, etc out of pieces of rough slate. It looked very cool and would be something I would do for my Leo if I had the time

I'll see if I can find some examples for ya.