var banner = new Array();

banner[0]='http://i49.tinypic.com/e851fn.png';
banner[1]='http://i50.tinypic.com/6j3n83.png';
banner[2]='http://i47.tinypic.com/k3kr2t.png';
banner[3]='http://i50.tinypic.com/i2slq9.jpg';
banner[4]='http://i45.tinypic.com/14u8har.png';
banner[5]='http://i45.tinypic.com/zmb5vp.png';

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