Hey there! I do work in Aseprite, but I don't include the Aseprite files, only PNGs and spritesheets with parsable metadata. The Aseprite files are actually typically not as easy to work with as you'd expect- This monster in particular has a lot of interchangeable parts and that means a lot of layers and special fixes for certain combinations. The export of the Aseprite file for every zombie combination was also done with a custom program that I wrote on my end.
I provide the PNGs and spritesheets only, minus the Aseprite file, for a few different reasons:
- Indie devs who use my asset packs can readily and easily use the PNG format in any engine, and edit them in any image editor (including Aseprite).
- I'm actively developing a competitor to Aseprite.
- I want to retain control over the original work if possible.
If someone desperately needs the Aseprite files because of a specific issue or workflow requirement (this is super rare) I deal with that on a case-by-case basis. I'm relatively confident that if you want to edit the sprites, it would be easiest to import the final product PNGs to Aseprite.