Do you remember the trick you have to use to seamlessly integrate Java3D and Swing? You now have this for free with JOGL and Swing. That means we can now do what Avalon does. Yes, we can actually composite 3D and 2D scenes easily. Get rid of your old icons and use fully animated 3D objects instead.
I cannot stress it enough: take a look at the demos and at Ken's and Chris' posts. On the following screenshots, the gears are rendered upon a Java2D gradient and two transparent Java2D pictures are drawn on top of the 3D scene. You can also notice there is absolutely no heavyweight/lighweight problem compared to Java3D. These guys rock.