Gallery Shortcode WordPress - Hacking Output

functions.php

<?php
/*
 * Change WordPress default gallery output
 */
add_filter('post_gallery', 'ct_post_gallery', 10, 2);
function ct_post_gallery($output, $attr) {
    global $post;

    if (isset($attr['orderby'])) {
        $attr['orderby'] = sanitize_sql_orderby($attr['orderby']);
        if (!$attr['orderby'])
            unset($attr['orderby']);
    }

    extract(shortcode_atts(array(
        'order' => 'ASC',
        'orderby' => 'menu_order ID',
        'id' => $post->ID,
        'itemtag' => 'dl',
        'icontag' => 'div',
        'captiontag' => 'dd',
        'columns' => 3,
        'size' => 'thumbnail',
        'include' => '',
        'exclude' => ''
    ), $attr));

    $id = intval($id);
    if ('RAND' == $order) $orderby = 'none';

    if (!empty($include)) {
        $include = preg_replace('/[^0-9,]+/', '', $include);
        $_attachments = get_posts(array('include' => $include, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $order, 'orderby' => $orderby));

        $attachments = array();
        foreach ($_attachments as $key => $val) {
            $attachments[$val->ID] = $_attachments[$key];
        }
    }

    if (empty($attachments)) return '';

    if(is_page_template('templates/partners.php')) {
        foreach ($attachments as $id => $attachment) {
            $image_alt = $attachment->post_title;
            $link = $attachment->post_content;
            $img = wp_get_attachment_image_src($id, 'full');
            $output .= "<$icontag class=\"col-md-2 col-sm-4 col-xs-6 text-center item\">\n";
            $output .= "<a href=\"$link\" target=\"_blank\" rel=\"nofollow\">";
            $output .= "<img src=\"{$img[0]}\" alt=\"$image_alt\" />\n";
            $output .= "</a>";
            $output .= "</$icontag>\n";
        }
    } elseif(is_home()) {
        foreach ($attachments as $id => $attachment) {
            $image_alt = $attachment->post_title;
            $link = $attachment->post_content;
            $img = wp_get_attachment_image_src($id, 'full');
            $output .= "<$icontag>\n";
            $output .= "<img src=\"{$img[0]}\" alt=\"$image_alt\" />\n";
            $output .= "</$icontag>\n";
        }
    } elseif(is_singular('album')) {
        foreach ($attachments as $id => $attachment) {
            $image_alt = $attachment->post_title;
            $img = wp_get_attachment_image_src($id, 'large');
            $output .= "<$icontag>\n";
            $output .= "<img src=\"{$img[0]}\" alt=\"$image_alt\" />\n";
            $output .= "</$icontag>\n";
        }
    } else {
        foreach ($attachments as $id => $attachment) {
            $image_alt = $attachment->post_title;
            $img = wp_get_attachment_image_src($id, 'large');
            $output .= "<$icontag>\n";
            $output .= "<img src=\"{$img[0]}\" alt=\"$image_alt\" />\n";
            $output .= "</$icontag>\n";
        }
    }

    return $output;
}
;?>