Other ideas using these glass balls:
~~drop in a little watered down paint and let your kids shake them.
~~add stickers (letters for initials are super-cute)!
~~for an "adult looking" ornament carefully stuff in an entire sheet of printed tissue paper (think animal print or something else out of the ordinary).
~~paint markers work great on these ornaments, so you can pretty much personalize them however you'd like!
I have about a dozen left, so we'll be crafting a few more this season; would love to hear your suggestions if you have any!!