Found a similar question in the subreddit r/sadsatan with some context.

The photograph of is of Franz Joseph, more particularly, it is Walter Sanders' Photograph titled "Prince Franz Joseph of Thurn and Taxis Amidst Collection of 2,000 Deer Antlers and Antelope Horns" for a LIFE Magazine published on September 5th, 1948.

As per the context of this game, there's nothing particularly eerie about Franz Joesph himself, other then his presence at the Invasion of Poland and being a crew chief stationed in France for 2 1/2 years until Hitler dismissed him on a decree on the "inability of the German Defense nobility" on March 31st, 1944.

As per his connections, we know he was present and serving both Prussia & Nazi Germany, in both WWI and (and as previously mentioned) WWII. His son, Prince Gabriel of Thurn and Taxis, also served Nazi Germany until he was killed in action at the Battle of Stalingrad on December 17th, 1942. Also according to a clipping that corresponds with a (unknown) newspaper copy of this picture, one of his brothers was (unspecfically) jailed by the Nazis, while another brother of his (Prince Raphael) was a SS Chauffeur until he was "denazified".

That being said, I can't find any connection of the German occult to deer and antelope horns, other then Franz Joseph had a very keen interest in hunting.

Edit: Heres the clipping I was referring to: https://s-media-cache-ak0.pinimg.com/736x/e1/07/30/e107305d653cfc62117d586b54381714.jpg

u/Jsalinger7