/**
 * Preprocess function for node.tpl.php
 */
function THEMENAME_preprocess_node(&$vars) {
  foreach (array_keys($vars['content']['field_images']['#items']) as $key) {
    if ($key > 0) {
      $vars['content']['field_images'][$key]['#access'] = FALSE;
    }
  }
}

Drupal 7