Refrigerator magnets !!! on tiles... Repeat for all of the tiles. As long as you move somewhat quickly, you'll have enough time to Mod Podge all of the tiles first, and then lay the pictures down. Once they're all coated, let them dry.
Craft Fair idea - clothespin fridge magnets Six for $5. Cost of supplies aprox. 40 cents. The packaging is so important! http://bluejellystampin.blogspot.co.uk/2012/07/ready-for-summer-crafting-show.html