Billiard balls can look great both on and off the pool table.
Ask the guy you see wandering the aisles wearing an apron at your local hardware store for the right epoxy to attach a billiard ball to a metal or wooden pole.
Pound the pole into the earth in your garden.
There are items around the house you can use for your pole:
Handle from broken broom, rake or other tool.
When the pole is set in your garden use your epoxy to attach a billiard ball. Group them together for an attractive arrangement.