Hey spyw, the outfits of the characters are on the spritesheets, as you can see them in the preview images. So there is currently no system with extra layers for the outfits.
However, the pack also includes a base / template character without any outfit to easily add your own. You can of course, also edit the outfits yourself.
Would you like different layers for the clothing / hairstyles to easily construct your own character? If there's demand, I'm happy to look into it in the future, so let me know what you need :)
Cheers