I've said before in interviews that I didn't want to write the Fever series, and that I had no intention of cooperating when the story idea began stalking me and wouldn't go away.
I had another Keltar novel planned. Don't get me wrong, I always intended to spin another series off my Highlanders, which is why I layered in all the complex background, but I had no idea the next series would be such a departure from what I had been writing until it was nearly done. By then it was too late to re-design and sell in a new cover.
Now you know where Darkfever's cover came from.