Image preloader

preloader.js

var imgs = {
        $wrap : false,
        $imgs : false,
        settings : {
                beforeClass : 'preload',
                triggerClass : 'visible',
                excludeClass : '.no-preload'
        },
        init : function() {
                var set = imgs.settings;
                this.$wrap = $('.content, .pbox-outer');
                this.$imgs = this.$wrap.find('img').not(set.excludeClass);
                var len = this.$imgs.length;

                if(len && s.isIe === false) {
                        this.$imgs.addClass(set.beforeClass);
                        this.$imgs.each(function() {
                                var $this = $(this);

                                if (this.complete) {
                                        $this.addClass(set.triggerClass);
                                } else {
                                        $this.load(function() {
                                                $this.addClass(set.triggerClass);
                                        });
                                }
                        });
                }
        }
}

to use:
imgs.init();
You can set
"beforeClass"( class for all images which are preloading),
"triggerClass" (class added after loading),
"excludeClass" (image with with class won't be preloaded)