Lots of ideas here: https://artfulparent.com/shaving-cream-art-play-round-up-of-ideas/
Here's an idea for decorating plain terra cotta pots: https://www.hometalk.com/28951674/marbleized-terra-cotta-pots-painted-with-shaving-cream
you might find this tutorial helpful - they recommend using ink instead of food coloring to make the project more durable https://abeautifulmess.com/2015/03/how-to-marble-with-shaving-cream-and-ink.html
Spread shaving cream on an old cookie sheet and drip colors of acrylic paint on it. Swirl the paint if you want with a paint brush or tooth pick. Then roll a vase, jar, or mug in it. I even have used hardboard canvas on them.
Here are some more ideas https://artfulparent.com/shaving-cream-art-play-round-up-of-ideas/