var banner = new Array();

banner[0]='http://almacen.navidaddigital.com/pic/usuarios/Carlota/D14YPS536D8E950.jpg';
banner[1]='http://imagenes.floguis.com/wallpapers/wallpaper-navidad-2.jpg';
banner[2]='http://spanish.people.com.cn/mediafile/200412/24/F2004122414305700000.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);