There is a picture of Reichenbach Falls above the mantle at Baker Street.
Roughly 12 minutes into the episode, Holmes is looking at photographs of potential criminals who may have stolen the Mona Lisa. The first photo we see dropped onto the desk is a picture of Sir Arthur Conan Doyle.
The originally story didn't make clear what Holmes's case with the French government was, let alone if Moriarty had anything to do with it. For this adaptation, it involved the theft of the Mona Lisa and was a crucial part in bringing down Moriarty's organization.
In the original story, Doyle is vague as to the specific crimes of Moriarty that Holmes foiled. The Mona Lisa was in fact stolen in 1911 by a Louvre employee. The plot attributed to Moriarty is based on an article on the supposed purpose of that theft published in the Saturday Evening Post. It has been largely discredited but a similar scheme was featured in the Doctor Who episode "City of Death" and in this retelling of "The Final Problem."
One of the few episodes with genuine narration.