Well, a Loader is itself a DisplayObject - so you could just addChild(event.currentTarget) and it'll show up just fine. It extends DisplayObjectContainer just like Sprite does.
If you literally need a Bitmap, then you can do something like:
var bmd:BitmapData = new BitmapData(event.currentTarget.width, event.currentTarget.height);
bmd.draw(event.currentTarget);
bitmap = new Bitmap(bmd);
And do it that way. You might have to tweak that a bit I'm going from memory.
If you're ever having issues with the Display API, this is a very good chart to summarize what lives where and how the various display object children are connected: http://accad.osu.edu/~pgerstma/class/pca/resources/as3API/AS3API-flash.display.png
Myk
2010-02-19 15:31:09