I'm not sure where I saw this idea, but I loved it! Christopher loves stickers and they make great rewards for chores and anything I want to reinforce. :-)
The original one I saw was made out of a heavy poster board. however I wanted something more durable. So I just cut a square out of a large box and covered the edges with duct tape. Then added foam stickers for his name. We posted it over his bed so his little brother couldn't get to it.