barleywine -
The code that makes Image Titles work is quite simple, and can be adapted to many situations.
PHP Code:
$title = (file_exists(DIR_WS_TEMPLATE . 'buttons/' . $_SESSION['language'] . '/boxhead-' . $box_id . '.gif') ? zen_image(DIR_WS_TEMPLATE . 'buttons/' . $_SESSION['language'] . '/boxhead-' . $box_id . '.gif') : $title);
Change $title, '/boxhead-' and $box_id to fit the conditions.
There may be situations where the output is controlled directly by a zen function and this code cannot be inserted neatly.