Last night I had a dream which I think could become an interesting fic.

The premise was that one of the people in a Hogwarts portrait was a criminal. His punishment for the crime (crime yet to be determined) was to be trapped in a painting for 100 years. The story goes on from there, but before I write anything I want to know if it is even possible that a person could be locked in a painting. How long has Azkaban been around? What forms of punishment were used before Azkaban? If anyone could offer some insight, that would be great!