I don't think the iconField will work for the purposes of loading images. The menubar expects a class IE ByteArray of image data since it instantiates it with the new operator.
You would need to create a new MenuBar.menuBarItemRenderer that knows how to load external image urls. This class needs to implement IMenuBarItemRenderer, you could also subclass MenuBarItem and override commitProperties() to create the Image and load it from the data's icon field.
thank u mike