Normally you would not have advertising posters and billboards at home but if you look at some of the vintage posters you see that many are simply beautiful works of art. Advertising posters have been around for a long time, but it was only toward the end of the 19th century when lithography was invented and it allowed advertisers to print colours and details cheaply; consequently the advertising poster became an important medium to advertise products and services. It also coincided with the start of mass consumerism and an increase of people in the Western World with a disposable income; therefore, there was plenty to sell. Talented artists who struggled to make ends meet soon realised that working on commission for advertising posters allowed them to earn money easily and quickly and that is why we have so many advertising posters done by major artists.
You are still able to choose from a large variety of posters and concentrate on a theme, for instance anything by Mucha or Toulouse Lautrec and the Parisian Belle Epoque, early movie posters, vintage travel posters or posters advertising bicycles or food stuff.
Although most people will look for reproductions, you can still find original vintage posters. Obviously the high profile posters would be difficult (and expensive!) to find but it is still possible to find original Art Deco and Art Nouveau posters by minor artists at affordable prices. If you are thinking of buying posters to display them at home, you are better off with reproductions, original vintage posters require a lot of care and might deteriorate quickly if exposed in the wrong light or temperature. You will also have to look for the right poster frame, you should be able to find poster frames from a few dollars each for basic models to expensive frames in a variety of designs and materials.