I recently added a battleship and 4 cruisers to my chaos fleet and I'm trying to figure out how to do it in the fluff. I added a Desolator variant that I'm calling the Despicable class battleship which is big on firepower with dorsal lances. I also added an Archeron heavy cruiser (my second), a Devastation cruiser (my third) and two Slaughter class cruisers (numbers 3 and 4 in the fleet).
I have a couple angles that I'm thinking:
1) Make them a small fleet that chooses to ally with the Black Storm. Advantage: I can paint them slightly differently.
2) Makes them a fleet that the Black Storm takes over through brute force. Advantage: they will match the rest of my ships in terms of paint scheme.
I was leaning towards #2 but I'm now in the #1 camp simply for variety. Trouble now is coming up with a decent paint scheme that is still complimentary and allows me to use the ships without feeling silly. I'm thinking dark blue.