It can be any (though, linoleum is bad..don't use that). Some people use a thin layer of sand under the tile (like sandwiched between the tile and the floor, completely covered by the tile) to make the heat transfer more evenly. If your tiles aren't heating at all, then you need a bigger heater or thinner tiles.
Do you have a digital thermometer? It might be helpful to get one if you don't. You put the probe right on the tile so you can get the temp your gecko feels on its belly. If it's between 93-98 you should be good. If it's cooler, you might need a different heat source (or different substrate)