function random_image() {
  var myimagespath = "./guitarimages/";
  var myimages=new Array();
  //specify random images below. You can have as many as you wish
  myimages[0] = "guitar1.jpg";
  myimages[1] = "guitar2.jpg";
  myimages[2] = "guitar3.jpg";
  myimages[3] = "guitar4.jpg";
  myimages[4] = "guitar5.jpg";
  myimages[5] = "guitar6.jpg";

  var ry = Math.floor(Math.random() * myimages.length);

  document.write('<img name="guitar6" src="' + myimagespath + myimages[ry] + '" width="537" height="256" border="0" id="guitar6" alt="" />	');
}

random_image();