Ideas for a theme for a pixel art pack?

I've been planning to make a pixel art pack and publish it to itch.io, Right now I wanted to get some ideas from others and not just myself. Here's a good one, let's say you have a 2D (or top down) pixel art game you're working on right now if you had to choose a art pack to help you out with the art (with a Creative Commons license) what type of art pack theme would you pick?

Personally, I go with fantasy.

Simply because the environments are more generic. More reusable.

As far as themes go. I look for a set that has the environments, objects, signs, doors, some animations, Environmental effects....

I stay away from anything with too divergent an art style. It should reasonably match the style of other art packs.

A beautiful art pack is useless if I cant supplement from other sources.

Thanks for the response, fantasy sounds interesting.