The seller will be banned if they get repeat infringements.
Make sure you only publish thumbnail images or superimpose a 'watermark' type name or logo across any larger images to prevent others re-using them off the listings.
Also make sure the items you sell have your name & copyright statement somewhere on the item itself as well as any packing note or documentation. eg.
Copyright (c) your name 2013
If you have only bought an item with reproduction rights and other people have the same thing, they have the same right to sell as you.
Unfortunately it is very likely that someone who buys an artwork on eBay will simply buy it and either copy it and sell many of them, or buy it and bump the price on it for resell.
You can't, once they have it they can easily copy it and can sell it on and on, that would probably be the only reason to buy it, to sell it
There will be more chances of duplicating same art work.
do you think ebay will disallow anyone to sell copies of artwork if you have the original? I'm going to be selling prints but how do I stop people copying and selling it themselves?