Note: I have no idea what one person meant by saying their images were hacked and used on a porn site? Just what kind of photos does this person have on eBay? I have NO photos of myself, and eBay requires no photos of yourself. So I have no idea what this person is talking about. You do need a photo of the item you are selling. But if handbags and porcelain plates are the type of thing that arouses people on a porn site, then maybe we are in the wrong business!?
Overall, I have to say that beyondthestargate's advice is right on and I especially like the blacklight marking system.