Storage Rooms are relatively rare, because they require a very large amount of space. While they sometimed can contain both Buggable Furniture and Containers, they are more often littered with Obstacles.
As with all other rooms, the layout of a Storage Room is randomly generated when the Hideout is first created. However, most Storage Rooms tend to contain one or more of the following pieces of furniture:
Each piece of furniture may or may not appear in each Storage Room you encounter. There may be more than one of each, as well.
Note that Stereos will always appear up against the north wall, while Lamps always appear up against the south wall. Cabinets will always appear up against any wall. All other pieces of furniture will appear away from the walls, although Couches can glitch and overlap with a wall occasionally.
A Storage Room is usually a good place to hide from enemies, given that it usually contains lots of furniture huddled together. If you're looking for a fight, or trying to stay low, head for a Storage Room.