Here's what I would do....... Not sure if it is the exact corrcet procedure though.
- bid on the pic (with no intention of buying) it to make sure nobody else wins it.
- email eBay to let them know about the fraud.
- By winning the auction, you'll have access to the sellers name/address. Send him a cease and desist letter (preferably from a lawyer).
I guess it depends on how seriously you want to protect your copyright rights to your work.