Poster

The  is a wall decoration used by corporations for broadcasting a visual message. The poster is a mass manufactured propaganda work conceived and executed by a corporation for use in their publicly owned property. Unlike the painting, the poster is not framed and is wall-mounted to a wall by an adhesive.

Ripper!
Ripper!, was a pre-War movie directed by Tim Cain, starring Leon Boyarsky and Jason Anderson. Posters are held up in front of the Rippers' hangout in Fallout.

Children Are the Future
In white text on a black background, the poster reads, "Children Are The Future/Good Citizens Raising Good Citizens.". This poster is used in the Vault-Tec Vaults. It can be found e.g. in Lone Wanderer's Apartment in Vault 101

Chinese propaganda poster
A Chinese propaganda poster featuring the Scoped Gauss Rifle. Translation: "Long live the People's Liberation Army!"

besides these two posters there many others posters and billboards most of them are vault related.

the importance of the posters is as far as known nothing there mostly decorative and nothing else.