The cover of the Beatles album "Let It Be" has a black border. The border on the cover of "Let It Be" hanging in Ned's basement constantly changes color, but is never black.
If only the possessions of the Flanderses that survived in "Hurricane Neddy" were the family tombstones, all of Ned's Beatles records and memorabilia would have been destroyed too. Remember that Bart mentions that John Lemon is a 40-year-old novelty drink, and that John Lennon made his joke about the Beatles being "bigger than Jesus" in 1966.