Characters' last names have been taken from Serbian language - Prigusivac means 'silencer', Bauk is 'boogyman', and Cetnik is a nickname for Serbian military during WW2 or paramilitary units during Yugoslav wars of the 1990s. However, these are never really used as surnames in Serbia or anywhere else.
Serial killer Chick Prigusivac (Jeremy Renner) has a life-sized poster of Jeffrey Dahmer on his cell wall. Renner played the title character in Dahmer (2002).
A highway sign seen during Heck's initial drive home lists two towns: New Pristina and New Sarajevo. Their namesakes are the capitals of Kosovo and Bosnia and Herzegovina respectively.
Prison scenes and some surrounding outdoor shots were filmed in Deer Lodge, MT. The Old Montana State Prison was temporarily renamed "New Pristina State Penitentiary" for the film.