Hi,

Here is a patch to allow themes to override the sevenup lightbox using a template .tpl.php file. The default template file provided by this patch replicate the behavior of the original JavaScript in PHP.

The downside is some added work on the server side as the template is rendered for every page even when not required. Possible optimization to fix this is to cache the 'inline' javascript from sevenup_init to a file loaded using drupal_add_js. This cache file should be invalidated when the setting form is submitted.