var banner = new Array();

banner[0]='https://i.servimg.com/u/f48/17/28/01/99/figura26.jpg'; 
banner[1]='https://i.servimg.com/u/f48/17/28/01/99/imagem11.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);