var banner = new Array();

banner.push('https://nsa27.casimages.com/img/2011/07/06/110706032101485250.jpg');
banner.push('https://nsa28.casimages.com/img/2011/07/06/110706033737325539.jpg');
banner.push('https://nsa27.casimages.com/img/2011/07/06/110706034812155515.jpg');

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