TL;DR
A sprite pack which completely overhauls the aestetical feel of the game.What?
By simply replacing sprites, the entire feel of the game could be changed. There are several themes which could fit very well with the game's mecanics.Steam punk: The game is alredy very close to steam punk so a few minor tweeks to make it look more victorian would likely be enough. Could be tied to some additional mod to make flying ships, or mods which make the game more steam focused.
Magic/Elvish: Replace mechanical structures with magical ones. Make things more vibrant and colorful.
Druidic/Nature: Similar to the one above, but more plant focused. Could be tied to mods which revamp the polution mecanic in some way.
Dwarven: Minor aestetic tweeks to make things more "stony" and square. Could be tied to underground focused, or other mods which increase the imporance of stone.
Futuristic: Make things cleaner and more plastiky, similar to the general aestetic of the space exploration space only buildings.
Authoritarian: Go full gallatic empire colonizer by just adding some faction flags here and there.
Alien: Could be basically anything.
Why?
While very work intensive to make, these art packs could attract a ton of attention to the game. Youtube videos with titles such as "Can I beat factorio as a mage?" would pop up everywhere. There are several games which release these aestetics packs periodically as a way to keep things fresh without changing anything mechanically.It could also be very interesting for people who dislike the aestetics of factorio in general due to being too bleak.
It could also encourage the development of additional mods to make mechanical changes to make the theme work better.
