Most of the psychedelic rock posters made in the late 1960s and early 70s were vertically oriented. Perhaps it all started with stapling them to telephone poles but even the earlier boxing style posters of the 1950s and early 1960s were designed this way.
If you have a horizontal space you need to fill there are two ways to achieve that. One is simply to find a horizontally-oriented poster. There aren't as many to choose from and so we have gathered them here for you!
The other option is to use several vertically-oriented posters and arrange them such that they together fill a horizontal space. You can do this by selecting and hanging individual pieces, or frame them together as we have done above and in some other presentations we are including here.