Terra Nauvis: The Ultimate Factorio Single-Map challenge.
Large total conversion mods.
Transportation of the player, be it vehicles or teleporters.
Augmented or new ways of transporting materials - belts, inserters, pipes!
New ways to deal with enemies, be it attack or defense.
Changes to the player's in-game appearance.
Changes to enemies or entirely new enemies to deal with.
Map generation and terrain modification.
Furnaces, assembling machines, production chains.