The stylesheets themselves don't need specific image directories since the images used in them are hard coded. The templates on the other hand may need specific images used in their layout. That's where these changes would be needed:
$config['images'] .= "/$tempstyle";
$config['imageurl'] .= "/$tempstyle";
$config['imagepath'] .= "/$tempstyle";
Just modifying these configure variables dynamicly will allow template specific images. This could be done with the stylesheets as well during the call to auth if you wanted stylesheet specific image directories.
