One thing that I have been doing for fun at some recent comic conventions I've gone to are what I call "original art puzzles". I make these by buying puzzle blanks from a craft store (these are blank white puzzle-thickness boards which are pre-cut with a die which leaves enough cardboard in the spaces between the pieces to allow the puzzle to hold together, but little enough that it is easily broken apart when desired), drawing Turtle head sketches directly on each puzzle blank with a large marker, and then breaking the pieces apart and packing them in a small plastic bag with a header card (below).
It's something fun and different from the standard sketch on paper or print, and I think it appeals to those people who like Turtles and puzzles.
At one of our joint appearances a couple of years ago, I had some blanks with me that I hadn't drawn on yet. Jim Lawson took one and drew a cool dinosaur on it, and gave it to me. Nice, huh? -- PL