Other Factions...

Awesome game, only one problem with it though. How do I play other factions than the 10 available? I would love to play the Lombardii and I thought that it would be possible to unlock the remaining factions by beating the game. I did this with Western Roman Empire however still no other factions. Is it possible to get them or not?

YoungToasty about Rome: Total War - Gold Edition, v1.2.1