var banner = new Array();

    banner[0]='https://i1104.photobucket.com/albums/h329/Eidori/Header-1.png';
    banner[1]='http://i51.tinypic.com/2ntvtl.png';
    banner[2]='http://i42.tinypic.com/hwan8m.png';

    document.getElementById('logo').firstChild.src= banner[Math.floor(Math.random()*banner.length)];

    setInterval("document.getElementById('logo').firstChild.src= banner[Math.floor(Math.random()*banner.length)];",17000);