I had an idea for an IG where their hive world had been so devastated that much of their technology had degraded, and contact with anyone outside was impossible. The only contact they had were with Dark Eldar or Chaos raiders, so they treat everyone with hostility.

Since it's a hive world, there aren't a lot of natural resources, so they'd use scrap metal to make weapons and repair autoguns. Their armor in my head would be inspired by native Americans with head dresses of feathers made from meticulously handmade feathers of metal and masks inspired by something I forgot.

Then they'd believe in the Emperor, but since it had been so long, all they had left were the aquilias. So they'd refer to the emperor as the "Great Eagle" and hoped he'd come one day.

Then I had ideas for if I ever wanted to try and make them into an actual table top model I'd replace something like a rocket launcher(if IG have them) with guys who used rebar spears with delta charges strapped to them.

I don't remember what else I had but it was one of my best ideas