Lots of short story material for inspirational background info set in the WH40K universe (plus some fantasy warhammer as well)
Incidentally... I once decided I'd write something for Inferno, but after the Inquisitor game came out none of the ideas in my story treatment seemed particularly innovative.
It started with a battle over an Imperial relic on an outpost world. A young chaos cultist - elevated to Marine status - carrying within him (unbeknownst to him) the soul essence of an original heretical general , friend to a still alive leader, hence the unlikely promotion (narrative cuts back and forth with bitter heresy prose, the cruel sanctuary of the Eye of Terror, Death to the False Emperor etc) - who is caught/entrapped by a female inquisitor. The protagonist has flashbacks to the primitive world he came from ("running through the fungal hardwoods"), before being spared/enlisted in a chaos invasion +gory trials +fleshy-dimension gates - and also a duel on a surreal Demon World. The "big reveal" is when the inquisitor character is torturing the protagonist and is then suddenly faced with a much greater menace entombed in the younger warrior, and is seriously out of her depth (massive release of chaos energy, maybe the protagonist escapes minus an arm or something).
I only had snippets written and the whole thing would have got a bit too cumbersome to write then edit down (the submissions were ridiculously small), not to mention that at the time Inferno/Black Library were very touchy about scenes set during the Heresy (perhaps cordoned off by authors like Dan Abbett for the novels). I think I was going through an unemployed/depressed period as well, which made finishing projects difficult. I think that there was a whole Slaanesh theme running through - everything was a visceral and luxuriant celebration of pleasure/pain experience. All a bit Hellraiser/S&M - perhaps not suitable for the kids.
On well. It was interesting trying to write within the constraints of the GW universe. I don't think Inferno would have paid much, even if they'd okayed it. Heh. It beats writing for Bella (looked into that as well) ;)