(This was previously posted yesterday as a guest blog on According to Hoyt. Good comments there, check it out.)
Ahem, would all the authors look at me? Ignore the howling mob of artists and illustrators bearing down on us with torches and pitchforks after that question was asked; I've got the gates close and the drawbridge up.
Thank you. Now, the first answer is another question: what is good art? You with the pretentious air, you sit down. This is not your moment to pontificate. You over there giggling and quoting Neil Gaiman's Make Good Art speech... sigh. You're actually closer than you know. Let's try a simple working definition. Good art for authors is an image that will catch a browsing reader's attention, communicate genre, tone, and theme, and lead them to click on the little icon and investigate your blurb to see what the book's about.
You over there, complaining that definition is marketing, not art? Just. Shut. Up. Or I'll throw you to the angry mob of commercial artists and illustrators who make such images for a living. Michelangelo didn't paint the Sistine Chapel out of some wild whim of artistic vandalism, he did it because he was paid to produce work to spec on theme.
Now, how do you find good art?
There are three ways to approach this.
1. Start with books you like, in the genre you're writing. You don't even have to buy them, just click the "look inside" feature and check out the copyright page in the front matter. Many indie publishers list their cover artists, illustrators, and cover designers there. (If they're not wearing all those hats by themselves, anyway.) Quite a few trad publishers put in the artist, too, though rarely the designer. (That's likely to be an employee.) This one is likely to be moderately expensive in terms of time and money - after all, you already know that the listed artists do sell their art for commercial use, and you just have to backtrack where and how much. On the other hand, you'll also end up having to sigh and filter out artists like Michael Whelan and Kurt Miller, because they do this for a living and charge prices that put them well out of our reach. Someday... Anyway, the artists run from $6 USD on a royalty-free site to $12,000 USD for custom oil painting.
2. Start by browsing the places that have art for sale, looking for things that'll fit. This is very expensive in time, but cheap in money. Where are these places? In person, check the artist's alley at your local conventions; you can browse portfolios (look at the art for sale) and ask artists about commissioning a custom cover, or buying the rights to use a piece they've already done as your cover.
Online, you can look at royalty-free stock sites. This is far cheaper than commissioning, as you pay one flat fee to download the art and use it as you wish in accordance with the terms of the rights agreement. This includes places like dreamstime, fotalia, photo morgue, istockphoto, etc. This option starts at free (morguefile), and then goes to around $6 - $20 USD.
Beware! For royalty-free sites, if you're wildly successful and sell more than a set amount of books, you are legally obligated to return and purchase a higher circulation license. Also, you are not buying the right to put the image on things for sale - so selling posters, t-shirts, or mugs with your book cover is right out, legally! If you try to make money on an image in ways you did not purchase the rights for, especially that that you are not compensating the artist for, don't be surprised if they come after you legally like you'd come down on a pirate site selling your books!
That said, it is by far the least expensive in money option.
3. Buy a pre-made cover from a designer. This already has the art purchased and the design work done, and costs less than custom because the designer did it on spec, hoping to catch a customer. All you have to do is tell them your author name, book title, and any minor tweaks if you want them, and it's all done. This'll take the time to skim designers, but starts at $50 USD.
Caveat! The designer got their work from somewhere, and all the restrictions on the rights they purchased still apply to you, when you buy from the designer! Also, make sure you're buying the right to use, modify, and possess (there's some more legal language, too, here) the cover design; If you hit bestseller, there should be no legal way for the designer to come back and demand more money, or assert legally that you don't own the finished product and they can yank it. (It's happened.)
Whatever you do, pay attention to which rights you buy or license. Not all artists, especially ones starting out, are savvy about this, just as not all authors are savvy about copyright, rights licensing, subrights, and territorial rights. The more rights you buy, the more expensive it's likely to be - for example, artists will often retain the right to sell the image (and often retain the original painting, if it's a physical painting, and sell it separately.) If you want exclusive use - nobody else can use this image - it's going to cost more than if they retain the right to put it up on a royalty-free site and earn more money from other folks downloading it. If you want the right to merchandise - to sell posters, keychains, mugs, whatever with the image as part of your cover design, that's going to be a fair chunk more, because now you're directly competing with the artist's main ways of earning income - namely, selling their image. And if you want to be able to sell the unaltered image - that is, to take their painting or design, and sell it yourself as though you were the artist - that's going to cost you as much as the artist thinks they could make from that image over the lifetime of copyright.
Protect yourself, protect the artist, and protect your ability to do friendly business in the future by learning about rights and making sure both parties are clear on who's getting what before money changes hands.