There are two different projects in this post, so scroll the way to the bottom!
Rock Painting Free Design
You could purchase a rock painting kit (at local craft stores and Five Below)
and it will come with everything you need. The kit is not necessary, however.
Below is what to purchase if you do not have a kit.
Rocks (river rocks are very smooth and great for painting)
Cups for Water
Plates for Paint
Squeeze various colors of tempera paint on a plate.
Make a plate of paint colors for each person.
Give each person a paintbrush, cup of water to clean brushes, and a paper towel on which to wipe brushes
Give each person a rock and have them start painting.
After they are finished painting their rock they can decorate with glitter, stickers, ribbon, or any other decorative items you have provided.
Lay rocks on paper towel to dry.
Rock Cacti in Pot