An illustrator will provide paintings, drawings, graphs, etc. and you can pay anywhere from $5 to several thousand dollars for original artwork.
A photographer could be you or another amateur, or a professional. A pro will probably want from $250 to $3,000. Renting props and hiring models will add to your cost. For the front cover, it’s really important that a photo be first-class. This is an area where an author with a contract from a traditional publishing company has a big advantage over a self-publishing author.
Stock photos and clip art are alternatives to just-for-you photos and illustrations. They cost much less -- maybe even nothing -- but are not exclusively yours. One instant indication of a self-published book is obvious clip art on a book’s cover. (It's more likely to be obvious to people in the book business than to readers.)
The term “clip art” (or “clipart”) goes back to the time when illustrations -- often for use in newspaper ads -- were printed on glossy sheets of paper and could be “clipped out” by the person designing an ad.
Today, most clip art is digital, and is purchased in large collections on CDs or DVDs or downloaded from the Internet. Clip art photos, illustrations and cartoons are ubiquitous, but be aware that some clip art is NOT supposed to be used for commercial purposes -- like books. There’s no need to risk an embarrassing and expensive lawsuit when high-quality art is available for very low prices, or even for free.
Free photos are available at various state and federal government websites ranging from New Jersey to NASA. Military services, the Library of Congress and the White House have plenty of pix, too. Many corporate websites have excellent free photos, but be sure to follow the rules for using and crediting photos. The Microsoft and Apple websites have fine free portraits of Bill Gates and Steve Jobs -- but don't put either photo on the cover of a book attacking Bill or Steve.
While most self-publishing authors do not have the budget to hire a photographer to provide custom artwork, you are more likely to get high quality pix from stock photo suppliers like Fotolia or iStockPhoto than from the mammoth clip art collections. Prices range from under a buck up to about $100. I usually pay $10-$20. Do your best to not choose a photo or illustration that resembles a widely known logo or one that has already been used on a competing book.
The cartoon on the cover of this book was purchased from Fotolia, but it’s so perfect that a custom-made cartoon would not be any better. If you want to write a book criticizing this book, go ahead. Co-author Sheila M. Clark and I can stand it. We’re tough.
Books about the same subject tend to use similar cover illustrations. In the case of publishing, it's usually a photo of someone writing, someone reading, or one or more books. All four book covers shown below use similar photos of books with their pages fanned out. The illustrations are very large and the pages open upward.
When using a stock photo, particularly for a book in a field where similar or identical stock photos may be used, have it modified so it looks a bit different. For this cover, the fanned book is inverted and tilted along with the text to suggest action, motion or flight. The illustration is much less important than the title. It is reduced to become a decoration and does not dominate the cover. Carina Ruotolo, my cover artist, even changed the color of the fanned book's cover to match the purple of the text.
The amazing Carina is a magician with Photoshop and changed a white-haired grandfather into a black-haired father for this book cover.
[below] Carina cropped and flipped the Mona Lisa -- one of the most famous pieces of art -- to give it a new look. We may have violated "The Da Vinci Code," but so far, da Vinci has not complained.