Вставляем в ХТМЛ- Вверх

Код:
<style type=text/css>
  .punbb .main .container, .punbb .section .container, .punbb .section .formal .container, .punbb .formal fieldset, #viewprofile li strong, #viewprofile li div, #setmods dd, .punbb .post-body, .punbb .post-links, .punbb .info-box, .punbb #pun-main .info-box .legend, .punbb .quote-box, .punbb .code-box {
    background: url(Адрес фона) transparent !important;
  }
.punbb td.tc2, .punbb td.tcr, .post-box, .punbb td.tcl, .punbb td.tc3  {
background: transparent;
}
</style>