var banner = new Array();

banner[0]='https://i.servimg.com/u/f35/11/75/67/96/ban_213.jpg';
banner[1]='https://i.servimg.com/u/f35/11/75/67/96/ban_me11.jpg';

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