Yeah, so all the images in a given a folder should be named as indexes. That is, you start with 1.png, and then 2.png, 3.png, etc…
Except if you have a category where you want to have an item by default (topdefault and pantsdefault for example), where you start with 0.png. But this is only relevant if you’re working on a base, so don’t worry about this now, always start at 1.png! 🙂