Our cart isn't really designed to support that level of customization; Development is considering improvements in that regard at some point in the future, but it's a low-demand feature with our target user demographic that generally isn't up to that level of Web design sophistication; our top aesthetic priority has been ensuring a consistent, dependable look and feel for the cart across the huge range and variety of browsers, sites, and native CSS treatments where the cart can "drop in and just work". Savvy CSS selectors with !important declarations can go a long way, and the cart customization method that we do support is documented here:
http://www.e-junkie.com/ej/help.custom-cart.htm
