var max      = 10;
  var nrImages = 1;
  function makeImages() {
    this[0]     = "http://www.festivalflamenco.com.br/publish/pub/img/fundo_home.jpg";
    this.length = nrImages;
  }
  function makeLinks() {
    this[0]     = "#";
    this.length = nrImages;

  }
  var vetImages = new makeImages();
  var vetLinks  = new makeLinks();
  var x = Math.round(Math.random()*max);
  var y    = max / nrImages;
  for(var cont = 1;cont*y <= max;cont++) {
    if (x <= (cont*y)) {
      document.write("<style>#miolo {background-image:url("+vetImages[cont-1]+");height:auto;} #galeria {background:none;}</style>");
      break;
    }
  }