How far from the Necro background do you want to depart? A few of us were kicking around an idea for a VSF Necromunda, called <<Die Welt der Toten Dampf>> using the same gangs pretty much, but instead of trading houses in the Imperial World of Necromunda, they would be rival treasure-hunting gangs in fin du siècle Europe (and beyond), controlled by the Earl of Cawdor, Count Orlock, Duc D'Lac, Goliath Corporation, Margravine von Escher and Mijnheer van Saar.
It never developed much beyond that, but there are a few Old West style Necro versions around that could be a source of inspiration.
If you're sticking to a more spacey-future wars theme but departing from the background, maybe your Necro gang is a space-pirate crew, like the crew of the Betty in Aliens IV, or Serenity in Firefly. You can shoe-horn anything in there.