Make your own coasters- tiles, adhere picture/paper to tile with Mod Podge and let dry; Spray a coat of clear spray paint and let dry; attach felt pads to the bottom. Doesn't have to be beer coaster either!
Photo tiles using resin. I started out with a trip to Home Depot. These tiles were only 19 cents each! It doesn't get much cheaper than that! And I bought a package of 72 felt mounting circles for about Not too shabby!