Instead of packing slips we've been including cardstock 'receipts' with each of the orders we ship. We write the recipient's name, circle the merchandise they purchased, and include a hand-drawn sketch featuring characters from the game (example: http://forum-files2.fobby.net/0012/7914/chimera.jpg )

It was tedious at first, but people raved about them. Eventually we wised up and started offering store coupons to the community's artists in exchange for drawings. It's really added value to our products and simultaneously strengthened our community. Win/win!