location ~* \.(gif|jpg|png|swf|flv)$ { 
  valid_referers none blocked *.lishengqun.com lishengqun.com ; 
  if ($invalid_referer) {
    return 403; 
  } 
}

valid_referers none blocked *.lishengqun.com lishengqun.com ; 判断域名来源 如果来源不为这几个则返回403；该判断可加在任意location下；

但仍可单独使用链接访问

如果去除 none blocked 则不允许单独使用链接访问

世间山河广，祝你得偿所愿！