var banner = new Array();

    banner[0]='http://tinypic.com/r/210ae0m/5';
    banner[1]='http://tinypic.com/r/ehxfyo/5';
    banner[2]='http://tinypic.com/r/htzkus/5';

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