not an odd question at all. if ya went to the gallery where the painting was held and made a sketch with yer pad (they don't allow photographs in general, for obvious reasons), then it's cool. but if ya got a download from the internet, it's almost certainly illegal for several reasons: 1. we don't have the right to redistribute or sell photos or drawings posted on the internet 2. the person who made the copy of the painting did so from a photo, which is an illegal use of said photo 3. the internet is based on theft. by my estimate, more than 90% of all internet traffic is illegal file transfer 4. tattoos have a peculiar kind of copyright protection that is very difficult to describe or understand (I ain't a lawyer)