var banner = new Array();

banner[0]='http://img199.imageshack.us/img199/9771/lostcanvasx.jpg';
banner[1]='http://img688.imageshack.us/img688/8172/chibis.jpg';
banner[2]='http://img404.imageshack.us/img404/2131/sdfsdfsdfasdasdasdasasd.jpg';

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