The link below is from the website of an Irish author named John Connolly. He wrote a book called the Dark Angel which features a 15th Century Boheimien Monastery called Sedlac (Pronuonced:
Said-Leh-ch). In Sedlac there is an ossuray - place where bones were collected at the time - in which various "artists" (of sorts) have created structures, sculptures and other decorations and artifacts using the bones of the dead. Some might find the idea sickening or sacreligious, I personally find it maccabre but fascinating at the same time, but it make for a very effective atmosphere.
There is a video also on the page that I've linked to (it's right at the top) in two different formats so you should be able to view it. Although the book "The Black Angel" is fiction Sedlac is real.
I thought that your mappers might want to have a look at it for some inspiration for a church or a chapel of some kind. It just seemed to fit in with the whole atmosphere and background of the 40K universe.
http://www.johnconnollybooks.com/journalism_sedlec.html