There is no foolproof way for eBay to do this. They could make it SLIGHTLY harder (block right-click) but that is so easy to get around it would make little if any difference. Understand that when you post an image anywhere online it''s going to be very easy to copy.
Recped is correct. There's not an image on the web, that I can't get a copy of.
I'm certainly not saying it's proper, but no image on the web is safe from being copied.
I think it would be a waste of Sixbit's time, to even try and prevent this.