What do I use to make a Wall Stamp?

[lovetoscrap]

I am not sure if this would go in the Crafts, Home Interior, or Scrapping board so I am just starting it here!

DH has time off for the holiday and is finally going to have time to paint our soon to be Disney themed bedroom. I am going to do a tone on tone Mickey effect on one wall and need to make my own stamp since I can't find one to buy.

What should I use to make the actual stamp? Can I just use a foam sheet? Is there something better? I want to make a very nice stamp since this is going on my wall. I will mount it on a wood block.

TIA!