As part of the User Agreement: 

When you create listings you give eBay and its customers permission, through our user agreement, to use your images, videos and product details. Your content may be added to the eBay product catalog, and may be used by other sellers in their eBay listings.

Also: 

When you provide content using our Services (directly or indirectly), you grant us a non-exclusive, worldwide, perpetual, irrevocable, royalty-free, sublicensable (through multiple tiers) right to exercise any and all Intellectual Property Rights you have in that content in connection with our provision, expansion, and promotion of our Services, in any media known now or developed in the future. To the fullest extent permitted under applicable law, you waive your right to enforce your Intellectual Property Rights in that content against eBay, our assignees, our sublicensees, and their assignees in connection with our, those assignees', and those sublicensees' use of that content in connection with our provision, expansion, and promotion of our Services.