var banner = new Array();

banner.push('http://i41.tinypic.com/2qlefs8.png);
banner.push('http://i30.tinypic.com/2nqsa4n.jpg);
banner.push('http://i41.tinypic.com/2qlefs8.png);
banner.push('http://i30.tinypic.com/2nqsa4n.jpg);
banner.push('http://i45.tinypic.com/ops2uf.jpg);

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