This was once, in a former life, an entire army of Warhammer 40K miniatures. It is now one of the greatest tributes to id's classic Doom I've ever seen.
There are the obvious conversions. Existing models modified and repainted to look like the bad guys from the game. But I love the extra touches. Like the pieces for door keys.
DOOM Daemon troops for Warhammer 40k [Next Level, via Super Punch]