Howdy,
You may wish to look at this thread: http://www.jehovahs-witness.com/12/107298/1.ashx
You may also want to see my first post in the thread. Some suggested that it is a conscience matter but I believe that that interpretation is incorrect.
The Society uses its usual circumlocution to express its denigration of tattoos without directly stating that tattoos are unfit for "true Christians" since it doesn't want to seem overbearing in such a scripturally vacuous area.
For all intents and purposes tattoos are still socially disapproved among Witnesses and one who got one while an active Witness would probably be subject to the same level of treatment and punishment as one who grew a beard/goatee, died their hair purple, etc. It would probably not be a disfellowshipping situation, however, unless there were other factors involved such as the actual tattoo image being a devil or something like that or other factors involving the particulars of the elders, locale, and persons involved.
-Eduardo