My wife watches kids for a living. Those kids like to color. A lot. I started gathering coloring pages online to print off for them all to color. It got out of control. I made a script to display all those coloring sheets. However, it took time to load each page. The kids did not have time for that garbage.
I switched gears and decided to lean into Isotope to make things easier. Now things are faster. I also utilize Print.js to make the printing process as easy as clicking on the image's tile.
Oh, to explain the name; my nephews call me Pepper (I have no idea why), and this is the polite way they ask me for more crap to color.
This project supports the following image formats jpg,gif,png,jpeg,svg,webp. You can add more on line 4 of index.php. This is set up so your images are in categories and/or subcategories. Following the following directory structure: images/category/image.ext or images/category/subcategory/image.ext. Everything should populate after that just fine.
Submit an issue. Feature requests are unlikely to be implemented as the project handles my needs just fine (for now).