There's no "theme" outside of minimalist, pixel-art! Look at some screenshots of Nira to inspire! Otherwise, let your imagination run wild!
Thanks for clarifying!
The rule "Games have to adhere to the theme and use minimalist pixel art to capture a big idea." gave impression there should be explicit theme.
Np! Sorry if that was confusing. Since Nira is a BIG game in a small package, games that capture that essence of the jam's theme will find ways to stretch every pixel into something larger than what's on the surface. Make the minimal magnificent!