window.addEventListener('load', function(event) {
  var availableImages = 4;
  var next_image = Math.round(Math.random() * availableImages) + 1;
  var image = new Image();
  image.width = "100%";
  image.src = "images/" + next_image + ".jpg";
  var p = document.createElement("p");    
  var p_id = document.createAttribute("id");
  p_id.nodeValue = "dynamic-background-image";
  p.setAttributeNode(p_id);
  p.appendChild(image);
  event.target.body.appendChild(p);
  //only for development
  var newLCountText = document.createTextNode(", Image: " + next_image);
  var image_count = document.getElementById("image-count");
  image_count.appendChild(newLCountText);
}
 , false);
 
  $(function() {
      $('#gallery a').lightBox();
  });