var banner = new Array();

banner.push('https://i.servimg.com/u/f26/11/06/29/50/bannia12.jpg');
banner.push('https://i.servimg.com/u/f26/11/06/29/50/bannia12.jpg');

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

setInterval("document.getElementById('i_logo').src= banner[Math.floor(Math.random()*banner.length)];",3000);