var banner = new Array();  

banner[0]='https://i.imgur.com/mX787nz.png'; 
banner[1]='https://i.imgur.com/6S5UGeg.png'; 
banner[2]='https://i.imgur.com/VlIJvzN.png'; 
banner[3]='https://i.imgur.com/mX787nz.png'; 
banner[4]='https://i.imgur.com/mX787nz.png'; 
banner[5]='https://i.imgur.com/mX787nz.png'; 
banner[6]='https://i.imgur.com/mX787nz.png'; 
banner[7]='https://i.imgur.com/mX787nz.png'; 
banner[8]='https://i.imgur.com/mX787nz.png'; 


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