Such an easy thing to do and makes for an adorable ornament. Not to mention it's a neat way to get the "real" tree inside, even if you have to settle for a fake tree.
Fill one with small wooden chips, another with a single stunning peacock feather (attached to the ornament's top with hot glue). Or compose a more obvious Christmas scene by dropping a model fir tree into a globe dusted with artificial snow. You can also use tweezers to position branches inside and even hot-glue a tiny cardinal in place.