The Oswald Wirth connection seems to be set up in the first film. At one point as Holmes is looking through the book which gives Lord Blackwood (now there's a name to conjure with) his power, the image on the left is given a nice full frame close-up;
http://img19.imageshack.us/img19/476/001vuc.jpg
It's a variant on the 'Sigil of Baphomet' from the 1897 book 'La Clef de la Magie Noire', by French nobleman and occultist Stanislas de Guaita. The interesting thing about this design is that it was the inspiration for the Oswald Wirth Baphomet design created in 1930 which is shown on the right. Even more interesting is that Wirth was de Guaita’s secretary and assistant, and may even have created the original engraving.
Also in the first film, Holmes gives us a Crowleyesque 'Hanged Man' while Blackwood opts for a more traditional interpretation;
http://img171.imageshack.us/img171/2897/002stv.jpg
There's also the fact that Oswald Wirth's card 15 - Le Diable, follows Eliphas Levi's Baphomet, and has on the right arm the word “solve” while on the left arm is the word “coagula.” This of course forms one of the dictums of Alchemy, and in Latin: 'Solve et Coagula' is 'Separate, and join together' (or 'dissolve and coagulate').
To me, this isn't a million miles away from Holmes' famous axiom; "When you have eliminated the impossible, whatever remains, however improbable, must be the truth."
Given Conan-Doyle's lifelong fascination for all things magical, mystical and spiritual, I can't help but wonder if there are more layers to the Sherlock Holmes stories than first meets the (private) eyes.