The picture is an entity in it's own right and ownership is the owner of the negative (or other original) unless they signed the rights away. Once published copyright is established, posting on eBay is publishing. Proving publication is another matter entirely.
There are rules of thumb that cover most situations but copyright law is extremely complex and hard to understand, it is a specialised area of law.
There have been attempts to exert copyright of items depicted in a photograph but in most cases they do not succeed - it depends on the usage in that case. So if you made and sold open source cola and include a photograph of a can of coca cola in your advertising you would be abusing coca cola's copyright, the same image used non-commercially would not.