Premade book covers are created by designers for self-publishing authors on a budget, who select the covers from the many that are available through a number of different sites. This means studying the market, discovering the genres that are most popular for authors, and creating covers that will dazzle not only them but their intended audience, and look great at thumbnail size on Amazon and other self-publishing sites.
Urban fantasy is an incredibly hot market with both self-published authors and their readers, and fun to design for. I've had incredible sales with paranormal romance and "shifters" (werewolves, but could also be any predatory animal).
I make these and many others available exclusively through SelfPubBookCovers.com
What I Did:
Book Cover Design