If you want to have an icon on the main toolbar (New Reply, Full edit) then you don't need a template edit.
Create a plug in at location "editor_toolbar_end" and insert the following code:
PHP Code:
$vBeditTemplate[extrabuttons] .= "<td><a href=\"#\" onclick=\"window.open('$vboptions[bburl]/photo_popup.php?e=$editorid','fotos','scrollbars=yes,resizable=yes,width={$vbulletin->options['photo_popup_width']},height={$vbulletin->options['photo_popup_heigth']}'); return false\" title=\"$vbphrase[photo_popup_insertlink]\"><img src=\"$stylevar[imgdir_editor]/photo_popup.png\" border=\"0\" /></a></td>";
The button will now appear at the end of the list.
Unfortunately there is no template hook for quick reply, otherwise we could just use the same technique