Some people on the boards here get the Alien Green paint chips from Home Depot, you know, the sample colors for the Disney paint? You could get 2, stick them back to back, laminate them, then just put them on with a key ring.
That will let other DISers know you're on the boards.
If you want to get really creative you could do a lot of things. Anything from drawing a simple Mickey Head with a black Sharpie marker, to making a design with fabric or felt.
How about doing the ribbon designs like there are pictured several places here? You know, on the T-shirts? that would definitely be unique.