var banner = new Array();

banner[0]='https://img4.hostingpics.net/pics/183814BanFF2.png';
banner[1]='https://img4.hostingpics.net/pics/701608BanniereFF3.png';
banner[2]='https://img4.hostingpics.net/pics/584125BanFF3.png';

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