I've got Favorite Nodes installed and working great, but I was wondering if there's a way I can add a little heart icon I made to the "Add to Favorites" link on nodes? I assume I'd need to modify the .module file, and I was thinking it was probably here

$links['add_to_favorites'] = array(
              'title' => t('add to favorites'), 
              'href' => 'favorite_nodes/add/'. $node->nid
            );

but I'm just barely getting my feet wet with PHP and haven't gotten anything to work right yet. Any help is greatly appreciated! My image file is "favorite.png" and it is the same directory as the .module file.