var banner = new Array();

banner.push('http://img73.xooimage.com/files/b/1/d/banni-re-1-2eb34a0.png');
banner.push('http://img74.xooimage.com/files/f/4/7/banni-re-2-2eb34d3.png');

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