Barbed wire across the forehead signifies a sentence of life imprisonment without possibility of parole (tattoos on the face usually signifies an expectation that the bearer will never leave prison). Barbed wire on the forearms or around the wrist signifies years served.
Churches, mosques, fortresses, etc. are often tattooed on the chest, back, or hand. The number of spires or towers can represent the years a prisoner has been incarcerated, or number of times he has been imprisoned. A cross at the top of the spire indicates that the sentence was paid in full. The phrase, "The Church is the House of God," often inscribed beneath a cathedral, has the metaphorical meaning, "Prison is the Home of the Thief."
and baby Jesus
indicates that the bearer is 'clean before his friends' in that he will never betray them to authorities.
: sex offender
Dagger in neck: Signifies that the bearer has killed and is available for hire to kill other prisoners.
: Worn on the knees: signifies that the owner will kneel before no man, or no one.
: Worn on the shoulders: Signifies that the owner is a man of discipline, status, and tradition. Men will also receive stars when promoted to "Captain" in the Vory V
: Signifies murder, if the murder was significant enough to merit the tattoo. Military insignia and uniform epaulets
are worn on the shoulders. This symbolizes criminal accomplishments. When a skull symbol is portrayed with it, it usually designates a man as a murderer. Epaulets are decorated with certain crests and symbols in the sections where one can see the skull there prior to conviction, especially when it was of any significance. (the list goes on...)
information courtesy of Wikipedia.