For the error I mentioned LoaderMax.getContent return a FlexContentDisplay but with rawContent setted to null (o.rawContent == null) :
LoaderMax.contentDisplayClass = FlexContentDisplay;
var queue:LoaderMax = new LoaderMax({name:"mainQueue", onProgress:progressHandler, onComplete:completeHandler, onError:errorHandler});
queue.append( new DataLoader(ba, {format:"binary", name:_imageName}) );
private function completeHandler(event:LoaderEvent):void {
var o:* = LoaderMax.getContent(_imageName);
}