document.observe("dom:loaded", function() {
    var imagesCollection=document.getElementsByTagName('img');
    for (var i=0;i<imagesCollection.length;i++)
    {
        if(!imagesCollection[i].complete)
        {
            imagesCollection[i].parentNode.addClassName('loading');
            imagesCollection[i].observe("load",function(){
               this.parentNode.removeClassName("loading");
            });
        };
    };
});