The pictures you make of your own items, whether photos or scans, are yours and other sellers cannot copy them without your permission.
Unauthorized use/theft of your pictures can be Reported to eBay. It is a Violation.
Some mischeivous sellers who have been plagued by this practice, will host their pictures off eBay , in PhotoBucket for example, and when they find a stolen picture, will switch the hosted image with another. Just what that 'other' might be depends on their level of annoyance and sense of humour.
