var banner = new Array();

banner[0]='http://i20.servimg.com/u/f20/14/10/57/30/logogc10.jpg';
banner[1]='http://i20.servimg.com/u/f20/14/10/57/30/logogc11.jpg';
banner[2]='http://i20.servimg.com/u/f20/14/10/57/30/logo_f10.jpg';
banner[3]='http://img821.imageshack.us/img821/1008/logogchupeleadebarcas.jpg';
banner[4]='http://img693.imageshack.us/img693/2797/logogchuullathorpe.jpg';

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