The Grand Alliance: Death is here, and with it quite a bit of background information. Take a look at the Deathlords: Masters of Undeath
You can see the leaked images here on Miniwars
via Mini Wars
Grand Alliance: Death from the next White Dwarf. Its basically fluff
-its ok- but the interesting thing is the Khemri Tomb Kings are missing. I dont know much about Warhammer End Times and what happened with them, just noticed that. There's another thing about these pics, its the subfaction treatment of every troop class between the undead.
Bits about Nurgle's new psychic powers (no pics, sorry):
blessing type: grant +3 to toughness for a friendly unit
curse type: negate snap shots for enemies when being target of an assault
Witchfire type: two psychic powers have AP2
other powers not mentioned yet.