When Fred and George are showing you how to climb and get the Beans, go to a corner of the rug in that room (furthest from Fred and George), and face the balcony that is all black on it. Enable the harrynormaljump code and you can now stand on the picture that hangs under the balcony. If you go back to the corner of the rug and enable the harrysuperjump code, you can land on the balcony and walk around. It is all black on top.