This post was published more than a few years ago (on 2013-05-02) and may contain inaccurate technical information, outmoded thoughts, or cringe takes. Proceed at your own risk.
I'm not sure exactly how I came into having these poster images, but reading on DigiBarn, it looks like they may have been designed by Marcin Wichary (perhaps this gentleman?) to commemorate the 20th Anniversary of the Macintosh.
You can download the entire set of 14 posters as PDFs, suitable for printing up poster-sized.