search in your details.php:
if ($image_allow_comments == 1) {
$site_template->register_vars(array(
and replace:
if ($image_allow_comments == 1) {
$site_template->register_vars(array(
"full_url" => $script_url."/details.php?".URL_IMAGE_ID."=".$image_id,
now you can write:
<a title="Add to FaceBook" href="http://www.facebook.com/sharer.php?u={full_url}&title={image_name}"><img border="0" src="{template_url}/images/facebook.png"></a>
mfg Andi