var banner = new Array();

banner[0]='https://i.servimg.com/u/f15/11/35/80/28/banwin10.png';
banner[1]='https://i.servimg.com/u/f15/11/35/80/28/baneau10.png';
banner[2]='https://i.servimg.com/u/f15/11/35/80/28/ban211.png';

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