var banner = new Array();

banner.push('http://www.vampyourspace.com/graphics/satan/1/1.gif');
banner.push('http://images.forum-auto.com/mesimages/405064/the-satan-pit-doctor-beast3.jpg');
banner.push('https://i.servimg.com/u/f24/14/94/46/40/parche11.gif');

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