The whole house is not decorated in comic/superheroes motif.
Various rooms are paying homage to various things from BB over the years. One bedroom is all about the "key" the houseguests receive when selected. The bathroom is a tribute to the rubber duck that is there every season. Another room (the lounge next to the bathroom) is decorated to highlight the "enduring" showmances from the series. Another bedroom is all about the "camera" since it is an important aspect of the game. Many black and white still photos from previous years are on the walls.
Only one room is the comic/superheroes, a bedroom.
