The Julian Kestral Mysteries by Kate Ross. Ok, the fourth book has a nice cover, but the first three I would redo. They do a good job at depicting a scene in each book, but I don't think they really represent the story itself. Perhaps if they had covers like C.S. Harris' Sebastian St. Cyr mystery series they'd have a bit more attention.
Mariana by Susanna Kearsley. The cover is nice, but I think this really beautiful story needs a really beautiful cover.
The Courtesan by Susan Carroll. Completely wrong century represented on the cover. The story takes place in the 16th century, this is not the 16th century!
Dark Road to Darjeeling by Deanna Raybourn. A little two Twilight-y for me. I wish this series could go back to the style of the original covers for the first two books. Those were lovely.
Cheri and The Last of Cheri by Colette. Yeah, I don't know who this is suppose to be on the cover, but it's not either of the two main characters: Lea, a woman in her 40s; or Cheri, a man in his 20s.
Hm, that's about all I can think of, for now.