The advantage of adding black decorations to our room is that we don't necessarily have to modify the color of the walls or the style that we have already chosen for that space. With two or three things on the list you add, you'll see a radical change.
Look at everything you could achieve.
A simple staircase will allow you to hang some Christmas lights and change the entire atmosphere.
A few simple pillows can make a difference.
You can paint the headboard and base of your bed.
A black cover will be the center of attention.
A carpet or a mirror like that.
Make it simple and everything will take shape.
You can add gold and silver tones in case you don't want it to be completely black.
Pictures, figures, books, pots, etc.
Place your black accessories on top of your furniture.
If you have an open closet, put only your black clothes.
Humor will never be badly received.
How about some beautiful flowers?