Actually, the producers of the old Batman TV series went to a lot of trouble to include this bit. I mean, their budgets were notoriously tight, yet they paid an artist to do that painting -- all for the sake of a gag which only a handful of people in the audience would have understood. Correct me if I'm wrong, but I believe that Skull and Bones did not become well-known to paranoids around the country until the 1970s.
Since S&B was founded in 1832, aren't the dates a bit off? Adam West was born in 1928, which means that the Bruce Wayne of the series must have been of a similar age. So his father Thomas Wayne probably would have been born in the 1890-1905 period. The grandfather would have gone to school well after the Civil War.