Itch already has comics, so why not add audiobooks/podcasts?  They're very popular, but no where near as bandwidth heavy as videos.

You can put audio books on Itch right now, in the Book category with an appropriate tag or in the Everything Else category. There don’t seem to be any audio books on Itch right now, so you could be the first!

The time to add a new category is after there are a good number of audio books on Itch, not before.

They're very popular, but no where near as bandwidth heavy as videos

Itch is not a media content hosting site, like youtube. You do not host videos on Itch. You might sell your indie movie here. But you do not upload your vlog here. Or a podcast.

An audiobook is not a primary media. One does not create the story in audio format. It's literally someone reading a book. An existing book.

Itch has 20000 items in the book category. I do not think, we need a category for < 100 items.

 https://itch.io/books/tag-audiobook

https://itch.io/books/tag-audio

But one might want to suggest to have a "suggested" tag for these. "suggested" tags are the tags that are in the list and will appear in auto-complete when typing a tag in the tag selector boxes.