re: Question regarding the end of Shawshank Redemption

The posters are also a nice plot device to add time/place to the story. In a prison movie especially, the audience can get bogged down and lose track of the fact that YEARS are passing Andy by while he wastes away in jail. By signifying eras of film, the posters give clues as to how many years have gone by since Andy first got to jail. Darabont did a good job with that and the music (Tommy going to jail with rock and roll playing, for example) in Shawshank to give his audience a timeline to follow.