In the shower niches, as a rule, installacrylic pallets, or lay ceramic floor tiles. Both options are good, but you can do a little more original, replacing the tiles with small pebbles collected on a rocky beach. The process of laying stones is quite tiring. And to collect a lot of stones about the same size is not so simple, but the result is worth it - it turns out very nicely. You can make a similar floor in the entire bathroom, but it will look cool in the shower room, and for the rest of the room it's better to tile.