Tattoo Artist? (in General)

Can someone please explain the abilities of the Tattoo Artist. I don't really get it.

(novice) It changes one type of familiar/tattoo/rune into another
(novice) using the type you're changing to as payment

If you have a large tattoo that you want to turn into another type, then you take that large tattoo and a base tattoo of the type you want and combine them to get a large tattoo of the type you want.

You can revert the tattoo back for a week but you won't get the base tattoo back.

http://www.carnageblender.com/wiki/Tattoo%20Artist