Hey Bob!
You should be good to go on that. Everything you did is completely eBay legal.

Like Marci suggested, I would make the banner and/or the text to your About Me page.
Here are the codes for each:
Clickable Banner:
<a href="http://members.ebay.com/ws/eBayISAPI.dll?ViewUserPage&userid=robertjohnston">
<img src="http://i113.photobucket.com/albums/n227/robertjohnston1/DadsBooks.jpg"></a>
Clickable Text:
<a href="http://members.ebay.com/ws/eBayISAPI.dll?ViewUserPage&userid=robertjohnston">Visit my About Me page!</a>
You can change the text to anything you want.