Theres the source of the blood, some poor guy attached the the ceiling. that also explains the Pilum (Roman spear) that Mathias is carrying.
Just out of pure side note, the famed "Spear Of Destiny" would have been a Pilum. No they don't have the "Spear of Destiny" Perhaps its a replica....

I need any artworks by next Wednesday so I can send the files off. If I don't get any by then I will throw something together and use that. I know there's been a few of you who are interested so if you cant get it done by then still do it and it will prolly end up in future books.