Preloading images is useful: Instead of loading an image when the user request it, we preload them in the background so they are ready to be displayed.

imagePreload.js

(function($) {
  var cache = [];
  // Arguments are image paths relative to the current page.
  $.preLoadImages = function() {
    var args_len = arguments.length;
    for (var i = args_len; i--;) {
      var cacheImage = document.createElement('img');
      cacheImage.src = arguments[i];
      cache.push(cacheImage);
    }
  }

jQuery.preLoadImages("image1.gif", "/path/to/image2.png");

//http://engineeredweb.com/blog/09/12/preloading-images-jquery-and-javascript