gistfile1.php

<?php
print "<ul class='full-images jquery-load'>\n";
$n = 1;
foreach ($data->_field_data['nid']['entity']->field_image_set[und] as $img) {
  $render = image_style_url('thumbnail', $img['uri']);
  print "<li class='full-image fullsize-item-" . $n . " jquery-load' data-full='$render'>";
  if ($n == 1) {
    print "<img src='" . $render . "' alt='" . $img['alt'] . "' />";
  }
  print "</li>\n";
  $n++;
}
print "</ul>\n";
?>