Retcon article
(covers information that was retroactively changed)
Lieutenant General Thomas "Stonewall" Jackson was a 19th century Human who served as a commanding officer in the Confederate Army under General Robert E. Lee during the American Civil War.
A painting entitled The Last Meeting of Lee and Jackson at Chancellorsville, which depicted Jackson (right) and Lee, during their final meeting on May 2, 1863, was stored in the USS Enterprise's library computer in 2254, and was among the materials viewed by the Talosians when they scanned the Enterprise computer. (TOS: "The Cage")
Although not mentioned by name in dialogue, the painting of General Jackson, appeared on a viewscreen of the library computer in the original 1964/65 version of the episode.
While left out of the retconned 2009 remastered episode version, Memory Alpha still considers the image a valid reference source.