I'm a big fan of an artist named Alphonse Mucha. He did a lot of work in fours, like seasons and muses and things. He also did one set that I love, called "Stars." It consists of the Morning Star, the Evening Star, the Polar Star, and the Moon.
I have all three stars, but I'm missing the moon, and so feel incomplete. Bear in mind that this is not a particularly well known artist, or artwork. I just went to www.Artposters.com, and look what's on their front page.