This project has actually been a bit of an extension of my Postcards from a Solarpunk Future project! Building out all the places and options for the players to explore has allowed me to write in way more worldbuilding than I could get away with in a normal fiction project (though the players won't see all of it). Similar to the postcards where each is just a picture and little worldbuilding essay, no plot. It's also let me focus on aspects of solarpunk that I realized really interests me while working on the postcards. Stuff like reuse, rewilding, deconstruction, and generally what rural areas might look like in a solarpunk world, especially current-day bedroom communities.
As for the art, I'd been running out of ideas I was excited about for the postcard series, but since starting in on this, writing all these new locations, I've found a bunch of new scenes I'm really excited to do the art for.
I wouldn't say it's critical to the campaign exactly, but the scenes and maps will be something the GM can put up on screen on Roll20 to set the tone and feel, or to help the players picture their surroundings. Character portraits might help them remember who's who.
As for a moral, I've definitely got things I want to explore: the motives for and consequences of a sort of negative peace, the shifting value of things like industrial waste based on use (and generally the very rare win-win where a waste product from one process becomes a useful input in another), the priorities of society and how it might look when one has very different goals than profits. Generally I want to explore what very rural places like my hometowns might look like when society has moved away from cars. And to generally tout values like thrift and reuse. But I'm not sure if I have a specific moral in mind.