Your spheres are wonderful. Have you ever tried putting a light inside the spheres? It will project the most wonderful shadows all over the walls and ceiling. I have had the best results using a 5w halogen bulb, but it was a bicycle headlamp that I modified. I have never found an ac halogen that uses less than 20w. Halogens seem to work best because of the intensity of light, but the heat they produce is a drawback.

If you ever want to experiment with a patina, you can achieve a great blue/green using household ammonia and table salt. Sprits the work piece with saltwater, or dip it water and roll the piece in tale salt, they rig up a tent with a plastic bag or some kind of enclosure where you can suspend the work. put a small amount of household ammonia in at the bottom of the tent and the vapors will chemically react with the table salt and copper. You can also give the copper a nice dark brown/grey patina using just ammonia. The blue green patina is somewhat fragile, but will stand up to time with a coat of krylon or some similar acrylic spray coating.