<img src="" id="headerImage">
<script>
function random_imglink()
{
    var myimages=[];
    //specify random images below. You can have as many as you wish
    myimages[1]="http://i.imgur.com/NMeu6Yh.png";
    myimages[2]="http://i.imgur.com/vtg0H0E.png";
    myimages[3]="http://i.imgur.com/bpYYdZN.png";

    var img=0;
    while (img===0)
    {
        img = Math.floor(Math.random()*myimages.length);
    }
    document.getElementById("headerImage").src=myimages[img];
}
random_imglink();
</script>