Im trying to create a character mod but I am using many images instead of a sprite sheet. How would I change the code from this example (https://gist.github.com/Penguin-Spy/ab9c81511791bb90243d3e8bec2dcbd5) to work with many images instead?

By "many images" do you mean a single image for each frame of animation? Factorio is designed to load from spritesheets, so I'm not sure that's possible. Each animation has one spritesheet per layer (running, running mask, mining, mining mask, etc.)
If you're having trouble creating a spritesheet, there's various tools to generate them automatically (such as https://github.com/fgardt/factorio-spritter which can also generate the Lua definitions), or you can ask for help in the Factorio modding Discord or on the forums.