1) The Book Cover Designer—They have one of the largest selection of book cover designs online with several different designers displayed on their website. You can choose from premade covers starting at $30 as well as custom book covers for a higher price. Here are a couple of my favorite premade covers from their site.
2) Damonza—Designers of eBook and print covers. They are a little bit pricier but their covers are incredibly professional looking. Here's a sample of some of their covers found in their portfolio.
3) eBook Launch: This website has a Premade Gallery for $99, a Dynamic Gallery for $249, and a Premium Gallery for $379.
4) Paper & Sage Design: This online book designer features book covers, bookmarks, business cards, web badges, and more. They also have premade designs for a reasonable price. Here are a couple of my favorites.
5) Creative Paramita: This designer has both premade and custom covers with premade ones running from $40 to $130.
6) Najla Qamber Designs: I absolutely LOVE Najla Qamber Designs. I've seen some of the custom covers they've done for a friend of mine and they are gorgeous! I love that they have premade covers but you can also work with Najla to create a cover that will directly reflect your novel.
Obviously, there are many, many more book cover designers out there, but hopefully this gives you a starting point. If you have a book cover designer you love, please share in the comments—we'd love to add to our list! Happy hunting! And Happy Thanksgiving! :)