Wood Paneling.
There's no quicker way to darken a room than wood paneling.
It will instantly transform a bright, cheery room into a 1978 TV den.
Wood Paneling, in our opinion, is like orange shag carpet for your walls.

Dark, dingy cupboards and paneling in an already small space. Combine that with a nasty hollow-core door and a cheap ceiling fan and you've got the makings of a very depressing corner of the house. Our word for this type of cheap tackiness is 'rental' - as in "That bathroom lamp is just a board with lightbulbs on it! Rental!"

Even light-colored wood can be incredibly dreary - here, it just makes the room feel cramped.

This long, dark room, would feel much more spacious with white walls and ceiling, and a floor lamp or two. Darkness in a restaurant is 'atmosphere', but in the home, 'atmosphere' should be optional.

It's a wetbar! Note the obviously fake front on the fridge, the ridiculous cast metal cabinet hardware, the dark brown switch plate cover, and the cheap particle board countertop.

In our own house, the entire stairway to the second floor, and the back hallway were covered with cheap nasty paneling, almost exactly like the stuff behind the wetbar pictured above. Someone obviously thought it was too dark, because then they painted the paneling white.
We've since removed all the paneling from the house.