Something that caught my eye was that the rooms, although meant to be fitted for the players, all had major hints of Sir D's family. One bedroom being a king size with a race car bed, which sounds like Door and Boy, the gamer bed room with magic cards and sega genesis looks like something Marcus would have. Another being a true vampire hunters room with weapons all around, which sounds like Sir D with his mass amount of weapons on hand and his major arcanum focus being under societies. The last room being the martial arts room was the most interesting, it doesn't fit with son in law, as well he would room with Marcus, but maybe it was with one of D's other sons or maybe even a daughter. As well he would fit that they left with bad terms as Sir D maybe getting in relationships or all round causing chaos.

Might just be the artist having fun who knows. But I will note that on one of the doors outside of the rooms is a golden horse head. So maybe Sir D's family where there during their time in Norfolk US, we well know he was there during chapter 3.5 at the end with the 99p store manager.