Код:

<!--- Cлучайная картинка в Шапке в HTML верх-->
<style id="RandImg"></style>
<script type="text/javascript">
(function (){var img = [
"https://i.imgur.com/Jq8o6kS.gif", //multilang gif
"https://i.imgur.com/0g0RXEe.gif", //ice_animated
"https://i.imgur.com/z0BuRmJ.png", //AZ_Oly
"https://i.imgur.com/VO7HKWZ.png", //Mai black
"https://i.imgur.com/C5LhGYz.png", //POTO
"https://i.imgur.com/JvKCYvT.png", //Mai green1
"https://i.imgur.com/dphVD4L.png", //Mai green2
"https://i.imgur.com/R9yioMj.png", //DQ1
"https://i.imgur.com/djbC1n3.png", //DQ2
"https://i.imgur.com/hBboWwm.png", //BS1
"https://i.imgur.com/fcpSXF4.png" //Alina+Shoma
//Последний элемент без запятой;
]; var elem = $('#RandImg'), i= Math.floor(Math.random()*( img.length));
var cnt = '<style id="RandImg">#pun-title {background-image: url(XX);</style>';
elem.replaceWith(cnt.replace('XX',img[i]));
}());
</script>

<style>
#pun-title {
    position: absolute;
    top:0px;
    border: none;
    width: auto;
    height: 250px;
    background-size: auto;
}

#pun-title h1 {
  display:none;
  height: 0px;
  margin: -1px 0px 0px -1px;
  } 
  
  #pun {
    margin: 150px auto;
}

#pun-navlinks {
  height: 40px;
  top: 225px;
  background: #479F9F; rgba(0,0,0,0.4);
  -webkit-box-shadow: inset rgba(0,0,0,0.6) 0px 1px 5px, rgba(255,255,255,0.08) 0px -1px 0px, rgba(0,0,0,0.3) 0px 1px 4px;
  -moz-box-shadow: inset rgba(0,0,0,0.6) 0px 1px 5px, rgba(255,255,255,0.08) 0px -1px 0px, rgba(0,0,0,0.3) 0px 1px 4px;
  -khtml-box-shadow: inset rgba(0,0,0,0.6) 0px 1px 5px, rgba(255,255,255,0.08) 0px -1px 0px, rgba(0,0,0,0.3) 0px 1px 4px;
  box-shadow: inset rgba(0,0,0,0.6) 0px 1px 5px, rgba(255,255,255,0.08) 0px -1px 0px, rgba(0,0,0,0.3) 0px 1px 4px;
  }

#pun-navlinks .container {
  background-color: transparent;
  color: #fff;
  }

</style>