Well, layout-wise, the key areas of the Hideout are: the Entrance, the Bar, a Library, a Bedroom, and Storage.
With a mansion, the first-floor could be the Entrance and Bar, the second-floor could be the Library and Bedroom(s), and the basement could be the Storage (and maybe add your crafter stuff there too).

For the walls, you could try the Country Interior Wall, Flame Interior Wall, or Masonwork Interior Wall, if you want that stone look.
For flooring, there's the Marble Flooring, the Masonwork Flooring, or the Stone Flooring.