Another use for saving images is to practice exactly recreating that look with your own footage, using the still as reference. Try it on various types of footage, from various cameras, with various white-balances to really understand the look.
Pick and image from your folder of looks you like, and practice putting that look on your own footage. Practicing on a variety of footage will give you real-world practice to be able to recreate the look, but since you’re on your own time not a client’s, you can reference the screenshot until you really get it perfect. Trying to match the still and breaking down how the look was created will also help you begin to dream up your own looks.