Eager fans wanting to get their hands dirty with code will find Total War: Rome 2 has become a lot more easier to mod with the release of the official Assembly Kit through the Tools section in Steam.
Though it's still in beta, the Assembly Kit allows modders to edit the game's database and variants, modifying textures, models, animations and campaign-game start positions. Exporters also open up the possibility of changing unit models and animations with third party software, a key milestone in previous Creative Assembly titles.
For those just starting out there is example data in the toolkit, and once done with your creation you can upload it directly to the Steam Workshop to show off, though you'll have to be creative in comparison to the ever-growing list already available. More in-depth information can be found at the Rome Wiki