Head to a Home Depot, Lowes, or another fix your home store. Find your way to the tile section and choose what you like. I would stay away from glazed/smooth tile. Otherwise they sell all kinds from slate tile to kitchen floor tile. I choose a rather rough kitchen/foyer tile to help with the dragons nails (from what I can tell it hasn't helped much as to keep them trimmed but I would like to think that it does). A lot of the time those stores will have someone that works there that will cut the tile for you if you need it to be cut. Just make sure you have exact measurements and account for the edges of silicone/liquid nails what ever you have holding your enclosure together.
