A little plugin for preloading background images (for spinners 'n stuff).

jquery.preload_background_image.js

(function ($) {
  function background_image_url($object) {
    var string = $object.css('backgroundImage'),
      url_regex = /[("]([^()"]+)[")]/;
    return url_regex.exec(string)[1];
  }

  $.fn.preload_background_image = function () {
    return $(this).each(function () {
      (new Image()).src = background_image_url($(this));
    });
  };

}(jQuery));