My boys loved this...............
I took some foam stickers my kids had and put them on some foam that my husband brought home from working that they were throwing away (I love how thrifty my hubby is!).
foam board or other material that is durable
What I like about this is that when they get bored of the foam stickers / stamp you can take them off & put different ones one - then you have a whole new stamper!
My oldest son's finished masterpiece!