https://mattepaint.com/academy/tutorial/creating-custom-shapes-in-photoshop/

Concept Artist, Josh Durham, uses custom shapes in Photoshop in all his work. It speeds up your process by orders of magnitude and is a fantastic way to generate new ideas for your work. Learn how to create your own custom shapes in Photoshop based on real photography with this quick series from Josh! Josh covers how to select a good image, prepare it for converting to a shape and then how to create the shape and add it to your Photoshop library. In the final section he covers briefly how he uses his custom shape library to build scene's quickly and generate early-stage ideas.