I keep imagining the cover with orange highlights, like "Ready Player One," with the words running vertically down the cover, but you're the professionals, so I'm open for any imagining.
The novel is set in a wasteland type world, so dry colors would fit best; however, there is a lot of contrast with the settings as certain parts are still lush and green. The sky is a dark and cloudy, threatening, and the colors blue, red, and purple are reoccurring as well.
I don't want you to be limited to depicting the novel's setting, though. Think of what's popular. Game of Thrones cover's are very simple, usually a single image that relates to the novel. I prefer clean and simple of complex and cluttered.