//create a new loader
this.loader = new Loader();
//tell the loader where to find the picture
this.loader.load("http://somewebsite.com/image.png");
//when the loader finishes loading, call the function 'onLoadComplete'
this.loader.addEventListener(Event.COMPLETE, onLoadComplete);

//===================================================
public function onLoadComplete(event:Event):void { //adds the image to a movieclip container
//===================================================
//create movie clip container
var thumbnail:MovieClip = new MovieClip();
//add image to container
thumbnail.addChild(this.loader);
}