No, I don't. I don't think ThemeDesigner has a border option. Perhaps you meant background image? I am not sure when they added the CSS but ThemeDesigner now has a full-page option. When combined with the cover option, it should fill the entire page. Either way, could you provide a link to the wiki? Especially if the appearance has been modified with site CSS already, I am definitely going to have to see what the specific situation is.