Today's challenge is to design a cover that will sell your book.
Your book should be designed to market itself. I'm not an artist, so all I'll say about the cover art is that it has to appeal to your target market. It has to intrigue them without giving away too much of the story, and it should identify the genre. I have mine professionally done by Expert Subjects, then I ask readers who haven't read the book yet, which cover appeals most to them. If your book will be an e-book, the cover has to be a clear image, not too dark or too busy, and the title be readable in thumbnail size.
Leave the cover front uncluttered - your name, the title, the intriguing art. The back cover should include, in order of importance, the blurb about the book, positive comments from a professional review if you have one, testimonials from readers, your photo and brief bio, website URL and "author of---" (your previous books, if they're in the same genre or a close one), the genre, and if they are e-books, your amazon author URL so they can find your other books. If it's non-fiction, indicate the reader benefits of the information inside (Learn to lead a healthier life, be a better---, etc.)
If someone types in the key words for your genre, will your e-book come up? Make sure you have used those keywords in your blurb, bio, and the testimonials you've chosen, as well as in your title. Don't necessarily compromise a great title for keywords, however; that's what your subtitle is for!
Your challenge is to check your book cover(s) to see if all these things are there. If it's too late to alter existing books, consider what you need to add to future book covers.