There is more to making a book cover stand out than most of us can begin to realize (that goes for the interior of the book, too). Even a commercial graphic artist is not the same as one who understands what works for book covers. If you don't have much money, save up, but you can find cover designers that aren't that expensive, particularly if you stick to a simple design, if you can lead them in the direction your mind is thinking so they don't have to do umpteen retakes of guessing, and if you have your own artwork or nice photos.
Carolyn Howard-Johnson has several good DIY books on marketing and even on self-editing so your pro editor won't have to charge you a fortune to clean up a mess. Here's her post giving some tips on cover design so you can confer intelligently with your designer: What You Should Know About Book Covers