OK there's a story:
''Berzerkers are Chaos Space Marines dedicated to the worship of Khorne. They are frightening, unrelenting warriors who fight with a manic frenzy to claim skulls for the throne of Khorne.''
They are preety close to this text, I have a blood gore mod, so in the game they're realy close to story :).
I was looking some units on games workshop web page, and I think, that some civilizations would be great in aom (Daemons of chaos, Tomb Kings, Beastmen, Lizardmen, Orks and Ogres).
With that I mean core units and some lords:).