Not too long ago my wife took a trip to New York and stopped by the MoMA. When she got back she told me about a piece she saw that she knew I would love, "The Park" by Gustav Klimt. I'm not usually a fan of German Expressionism (although I do love German Expressionist films), but I absolutely love this painting. I have to go see it in person at some point.
While it was painted well before anything you could call mid-century, I think a print of "The Park" would look great in a mid-century home. Especially if you have the popular mid-century interior wall color of gray. Those greens would just jump right off the wall.