var banner = new Array();

banner[0]='https://i.imgur.com/sOwqSag.jpg';
banner[1]='https://i.imgur.com/vDHEij4.jpg';
banner[2]='https://i.imgur.com/t1bq0ui.jpg';

document.getElementById('pun-logo').firstChild.src= banner[Math.floor(Math.random()*banner.length)];
setInterval("document.getElementById('pun-logo').firstChild.src= banner[Math.floor(Math.random()*banner.length)];",3000);