I did this a few years ago with my son's school picture. We also wrote on the back side of the ornament the year and his age. Grandparents loved them. I copied the picture on to sort of heavy weight paper, you have to roll the picture to get it in the glass ball. Chop sticks come in handy for this process. You can use any kind of glass ball.
Wow this is adorable. Every time something memorable happens throughout the year, write it down and put it in the jar. On New Year's Eve, open the jar and reminisce about what a beautiful year it was. You'll realize how much you have to be grateful for and remember why the year was so amazing <3