Using Python's pillow library, Pixelate is a tool for creating pixelated versions of images programmatically. I made it for a class project at BYU. You can see some of the images the program creates here.
To run the program yourself, clone the project, then run python3 main.py
from the command line in the root directory. You'll need to edit the parameters of the function call at the end of main.py. Also add a directory with your starting images and another directory where the final images will be saved.
I'll edit this program at a later date to improve the process of creating/saving the images...