After the Storm-Trooper army list, your power armored space goons obviously need somebody to fight.
What better than space orcs then?
15 ready-made units (with points values), ready to fight, raid, pillage and occasionally confound your best-laid plans.
They're of course fully compatible with anything from the main book, so don't be afraid to have your orcs fight WW2 Soviets or the Klingon from Star trek.