var bgArr = ["/wp-content/themes/museoguatelli/img/ruote.jpg", "/wp-content/themes/museoguatelli/img/barattoli.jpg", "/wp-content/themes/museoguatelli/img/automobilina.jpg", "/wp-content/themes/museoguatelli/img/contenitori-vetro.jpg", "/wp-content/themes/museoguatelli/img/esterno.jpg", "/wp-content/themes/museoguatelli/img/macchinina.jpg", "/wp-content/themes/museoguatelli/img/orologi.jpg", "/wp-content/themes/museoguatelli/img/scarpe.jpg", "/wp-content/themes/museoguatelli/img/secchi.jpg"]; //and so on...
var i=0;

// Start the slide show
var interval = self.setInterval("swapBkgnd()", 5000)  

function swapBkgnd() {
 if (i>(bgArr.length-1) ) {
  i=0
  $("#menu-home").css("background-image", "url("+bgArr[i]+")");
 }
 else {
  $("#menu-home").css("background-image", "url("+bgArr[i]+")"); 
 } 
 i++;
};