The 11 tattoos are: The Avengers 'A', Black Widow's hourglass, Captain America's shield, Fantastic 4 symbol, Punisher's skull symbol (shoulder and half-sleeve versions), the SHIELD logo, Spider-Man's spider symbol, Venom's spider symbol, Winter Soldier's star, and the X-Men logo.
XCOM 2 appears to reverse the left arm tattoo for the right shoulder, so assymetrical logos like the Avengers and Fantastic Four logos should only be used on the left arm. All the others are more or less symmetrical and can be used on either arm. There's a bit of stretching going on in the UV-Mapping on characters' shoulders (especially the male)and I had to squash most of the logos vertically to make them look correct in-game.
More than happy to add more if any-one has ideas for additional tatts.
My other tattoo sets for XCOM 2:
Frank Frazetta Tattoos: http://www.nexusmods.com/xcom2/mods/567/?
My Voicepacks for XCOM 2:
The IT Crowd Voicepacks: http://www.nexusmods.com/xcom2/mods/535/?
CATE ARCHER from No-One Lives Forever 1 & 2: http://www.nexusmods.com/xcom2/mods/551/?
S.H.O.D.A.N. from System Shock 2: http://www.nexusmods.com/xcom2/mods/419/?
THE H.A.R.M. HENCHMAN from No-One Lives Forever 1 & 2:http://www.nexusmods.com/xcom2/mods/553/?
MONTY PYTHON Voicepack:http://www.nexusmods.com/xcom2/mods/560/?
BASIL FAWLTY Voicepack: http://www.nexusmods.com/xcom2/mods/546/?
ARCHER Voicepack Series:
Sterling Archer: http://www.nexusmods.com/xcom2/mods/499/?
Lana Kane: http://www.nexusmods.com/xcom2/mods/494/?
Cheryl/Carol Tunt: http://www.nexusmods.com/xcom2/mods/481/?
Pam Poovey: http://www.nexusmods.com/xcom2/mods/472/?
Dr Algernop Krieger: http://www.nexusmods.com/xcom2/mods/466/?
Malory Archer: http://www.nexusmods.com/xcom2/mods/477/?