In the Gold & Silver versions of the Pokémon gameboy game, you can get many cool items to decorate your bedroom by using the Mystery Gift, such as different beds, game consoles, dolls and posters:  

This table shows some of the items you can get. Usually, the cuter, bigger, and/or cooler they are, the more difficult they are to get. For example, a Shellder doll is not as difficult to get as a Squirtle or Bulbasaur doll. The beds, carpets and big dolls are all very rare.

Beds	Carpets	Big Dolls	Posters	Plants	Game Consoles	Small Dolls

We'll be adding more items as we hear of them.