IMHO, with the digital revolution, the best marketing plan is to post the pictures to a website (with 'proof' watermarked on them), and offer them to participants, announcing that they are available on some of the forums like this one. Yeah, you have to look at a lot of pictures to find your car, but it brings back some great (maybe) memories from the event, you only get what you really want, and the customers don't feel harassed!

Jeff Loewe from Cincinnati does a great job at Mid-Ohio.