var sfondi = [];   

     var bgurl =  sfondi[Math.floor((Math.random()*sfondi.length))];
     document.getElementById('home-banner').style.background="url('"+bgurl+"')";

     setInterval(function(){
           var bgurl =  sfondi[Math.floor((Math.random()*sfondi.length))];
           document.getElementById('home-banner').style.background="url('"+bgurl+"')";
           //$('.head-img').css('background', "url('" + bgurl + "') !important");
     },5000);