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!
Turn Tiles into Coasters by Stamping them with Paint! Have some Christmas stamps? Get some inexpensive tiles. Probably after they are thoroughly dried would be smart to give a couple coats of a clear sealer, so ink lasts.