I got this little peacock from a craft fair in Brazil. You could easily purchase small objects or pick them up for free (ex. shells, rocks, etc.).
Attach your souvenir of choice to the inner lid with super glue. Fill the jar with water. Add some glitter and a few drops of glycerin. The glycerin will allow the glitter (or "snow") to float around the jar when the jar is shaken. Screw the lid tightly and decorate the outside of the jar as you see fit.