I thought I had seen the whole internet but I am so late to the majesty of Boris Bucan's posters. I really like his bold use of line, pattern, and color, and I think his compositions are still relevant to today's graphic design trends, though they were created decades ago.
Born in Zagreb, Croatia, Boris is also a talented painter and mixed media artist. He has had numerous exhibitions around the globe, and was awarded the Lifetime Achievement Award by the Croatian Designers Society in 2006. His work can be found in prestigious arts galleries and museums, including the Victoria and Albert Museum in London.
[h/t: But Does it Float]