You're not going to get anywhere being nice and e-mailing eBay. You have to hit them where it counts -- the legal department.
Google is the same way. Their attitude is that they're so big, we don't have to worry about copyright violations from individuals.
A couple of months ago, Google web site was displaying a picture stolen from one of my web sites. After getting zero satisfaction through e-mail, I found a sample DMCA letter on the internet, modified it to suit my situation, and sent it off certified mail to their legal department. A few days later, the offending web page was gone, and week later I got a paper letter back from their legal department stating it had been removed. I can send you the letter I sent to Google, if you'd like inspiration for your eBay problem.
eBay (and everyone else) is required by federal law to respond to DMCA complaints (valid or otherwise) by immediately removing the content, then giving the poster a chance to appeal the removal. It's not always fair, but for the infringed photographer it's useful.
In a separate Google-related incident: Another web site to watch out for is eCanadaNow.com. It appears to be a web site run by a college kid in small town Canada that scours news web sites for stories and then posts them as its own. This wouldn't be a problem, except that Google has decided that it's a reliable, trustworthy news source and frequently links to it directly from news.google.com.
Imagine my surprise one day when casually surfing Google news I saw one of my photos illustrating a piece of "eCanadaNow" wire copy. The image wasn't merely deep-linked from my web page -- it was actually downloaded, re-scaled and hosted on eCanadaNow's web server. They even left my watermark intact (duh!).
Since the DMCA doesn't apply in Canada, I sent the kid a bill. When he didn't respond to it in a month, I sent copyright complaints to his host, his host's provider, his registrar, and anyone else I could think of. I also called the number in his whois record, which happened to be a relative's home and explained to them what was going on, and I sent a copy of the outstanding bill to that relative's address.
Two weeks later -- a Canada Post money order arrives in my mailbox. Justice is served.