When I decided how I was going to bust through the Dark Vengeance set, I decided to work on Chaos second.  First off, it's the larger of the two forces.  Secondly, it has a ton of duplicate cultists with not quite as much detail.  I spent most of the time with the Helbrute, the Lord and the Chosen.  I went with a purple and indigo color scheme to use some different color patterns than my usual work.  It's more Tzeentch and Slaanesh - ish work, but I like how it turned out.