Tile is so cheap! These tiles were 34 cents each at the hardware store. You can get 20 cent ones that aren't distressed on the edges. Martina made these using felt sticky-back round pieces (40+ pieces for $5.99) on the back and Stays-On (around $8) ink stamped with a rubber stamp on the top of the tile. She also sealed in the ink with some mod podge once it was dry. The dark brown one was smeared with Stays-On and then embossed. Don't they look classy? I love the stamp she used.
You can also use flat pieces of felt glued on the entire back surface of the tile. Overall the start-up cost for this project is a little much, but once you have the Stays-On ink and the felt pieces you can make a lot of tile coasters.