From the website polish-poster.com:
After World War II Polish society gradually began to regard poster design as an art form equal in importance to painting. On the one hand there were political propaganda posters drawn from the Soviet influence, and on the other were posters on cultural topics, particularly films as people flocked to the movies. Movie posters that evolved were unlike most in that a scene was rarely shown. Instead the artists tried to capture the essence of the film or use a visual metaphor to sum up the impression of it. This trend caught on and spread to other fields. Posters became an outlet for individual artistic expression Henryk Tomaszewski defined what later became known as the Polish School of Poster Art – Polish poster school by basing his work on artistic statement and on graphic interpretation of the film. Jan Lenica and Wojciech Fangor were among the first to introduce painters’ tools to poster design through use of texture and strong color masses and freedom with which they shaped their images. The posters of polish poster school, the height of the Polish school of poster art, were full of life and deeply humane content. So distinctive was Polish poster art that it became recognized worldwide.
There are a ton of amazing Polish movie posters to check out here.