var max      = 10;
  var nrImages =  7;
  function makeImages() {
    this[0]     = "/img/teste/1.jpg";
    this[1]     = "/img/teste/2.jpg";
    this[2]     = "/img/teste/3.jpg";
    this[3]     = "/img/teste/4.jpg";
    this[4]     = "/img/teste/5.jpg";
    this[5]     = "/img/teste/6.jpg";
	this[6]     = "/img/teste/7.jpg";
		    this.length = nrImages;
  }
   var vetImages = new makeImages();
    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("<img  src="+vetImages[cont-1]+" border=0></a>");
      break;
    }
  }