Lamé curves, super ellipses.
This is https://www.spoonflower.com/designs/10587231 Designed on my iPad using Procreate and Patternish softwares. Please contact me if you’d like to see this design in a different scale. For Green - https://www.spoonflower.com/designs/10524348-green-white-rhinestone-belt-buckle-by-gargoylesentry For Indigo Blue - https://www.spoonflower.com/designs/10504001