I found that through gameplay if I cheated the skill the tattoos don't appear until you earn the skill through gameplay. That said, I am sad to find out the unlocked tattoos do NOT transfer if you upload to gallery. I unlocked every tattoo but I can't transfer to another save which is a huge bummer. I hope to find a cheat soon. Also very bummer, all the unlocked tattoos are only available in CAS to the sim not their household :/ I have to edit the household's tattoos through gameplay. Maybe a mod will happen.
Edit: I also cheated down my earned skill in order to get the poor tattoo on every body part. I guess it makes sense all these ugly townies have to stay with their creator. 😄