var banner = new Array();

banner[0]='http://i45.tinypic.com/2wexu83.png';
banner[1]='http://i45.tinypic.com/2eg4u1f.png';
banner[2]='http://i45.tinypic.com/binjuv.png;

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