Tinkering away at my Dark Imperium models and a few other bits, I started piecing together who my Death Guard are and how they operate.
My main idea at the moment is that the background will revolve around “The Seven Hands of Fate”, a sort of small council of the Lord of Contagion and his six most trusted advisors. A sort of Mournival or Nurgle. At the moment the composition of the Hands is the Lord of Contagion; two Malignant Plaguecasters; the Noxious Blightbringer; a Warpsmith; a Chaos Lord of the Purge aka commander of cannon fodder); and, an Alpha Legion sergeant in charge of the army's Traitor Guard and cultist contingent.
The composition of the Hands will vary over time, they won't be all the characters in the army but they represent the ones the Lord of Contagion has the most faith in at that moment. Needless to say, being kicked off the council is not a good sign for one's odds of survival beyond the next battle.
The Librarian leading my small contingent of Fallen is constantly trying to maneuver his way onto the council. Right now he is trying to displace the Alpha Legionnaire. I just like the idea of two representatives of the Most Sneaky Legions in a battle of wills.
The Traitor Guard aren't themselves Nurgelesque but my old Chaos Undivided Lost and the Damned army now working as mercenaries being rented out to the Death Guard by the Alpha Legionnaire.
The Purge are feeling happy to be included and blissfully unaware that the Death Guard consider them mongrels barely suited to a station in life as cannon fodder. On a practical level they just exist so I have an excuse to use some units that don't quite fit the strict theming of the Death Guard. Raptors, basically, I want Raptors and the Death Guard don't do dedicated assault troops.