I would try changing includes/modules/CUSTOM/additional_images.php to change all your divs for additional images to a fixed width, rather than a 'computed' number... which is trying to spread your images across the page...

line 102;

PHP Code:
    // List Box array generation:
    $list_box_contents[$row][$col] = array('params' => 'class="additionalImages centeredContent back"' . ' ' . 'style="width:135px;"',  'text' => "\n      " . $link);