Some authors don't seem to have a lot of luck when it comes to originality in their cover designs. One such is Deborah Lawrenson (who I've never read). When her The Art of Falling was republished in 2005, it ended up with a tinted version (with added castle and bombers) of a cover image used on a Penguin Classic of an excellent H. E. Bates book the previous year.
The same thing happened to this book's original cover: the same image as appeared on it (again with bombers added) has also been spotted on the cover of Thomas Cahill's Mysteries of the Middle Ages.
Then there's her most recent book, Songs of Blue and Gold, which has the same cover as the German edition of a novel by Stephanie Gertler.