Only the very lightest of backgrounds.
My Iron Warriors are part of the 7th Company. They're reasonably friendly with Abaddon, and will go into battle with him and other legions (I have three squads each of PMs and 'zerkers, and imagine I'll paint up new squads as other legions as trades allow).
My Jenen Ironclads (lifted the name from Codex: Eye of Terror) are armoured-company traitors who are allied with the Iron Warriors. They do like salvaging Imperial gear and turning it to their own use, so while they primarily have the older gear, they do run into the odd new bits.
I don't need much more than that, given that they're canonical groups... they do what Chaos does, which is invade planets, kick tail, and then divide up the plunder.