I haven’t figured out how to remove a banner, but I can show you how to hide one. From a response to a similar question in the eCommerce Gem Plus section I got the selectors. From David Shariff’s website I found that the following CSS gives you an 80% transparent banner:
The first item is the default; the second is for well-behaved browsers; the third is for IE6/7; the fourth is four IE8. The first item is fully transparent, the others are 80% transparency. Thanks to tech support for the location in the product’s CSS and all credit to David Shariff for the CSS. Please see his blog for additional details.