var banner = new Array();

banner.push('https://i.servimg.com/u/f25/12/35/80/54/entete13.png');
banner.push('https://i.servimg.com/u/f25/12/35/80/54/entete12.png');
banner.push('https://i.servimg.com/u/f25/12/35/80/54/entete10.png');
banner.push('https://i.servimg.com/u/f25/12/35/80/54/entete11.png');

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