Random publishing thought for the day: never, ever get stuck with a bad book cover. Certainly, cover aesthetics are to a certain extent in the eye of the beholder, but if you want to see some covers that are O HOLY GOD MY EYES MY EYES bad, visit the Lady Aibell section over at Smart Bitches, Trashy Books. O my eyes.
Kids, I don't care if you're writing horror erotica. I don't care if you're writing in a genre ghetto to beat all genre ghettos. I don't care if all your friends have awful covers: don't let a cover like that happen to you. I've seen covers that were intentionally ugly (notably The Best of Crank! Magazine) but mostly cover-ugly is unintentional.
We all hear it: don't judge a book by its cover. But ya know what? Everybody does it. Big chain bookstores like Barnes and Noble and Borders regularly make their purchasing decisions based solely on how a book's cover looks. If they think it'll appeal to readers, they buy more. If they think the cover's crap, the might not buy at all unless you have a very solid sales record. In the end, if your book has a bad cover, most readers won't bother to pick it up at all.
How to avoid a bad cover? First, educate yourself about the basic principles of good graphic design so that you can communicate with artists/art directors on their terms. Study some classic art if you haven't done so before. If after that you still find yourself unable to tell good from bad ... find an aesthetically-sensitive friend you can rely on. Second, avoid dealing with publishers who put out bad covers. If this is unavoidable, do your utmost to steer them in the right direction -- and if you're dealing with a small press, they should be entirely steerable. If you're with a bigger publisher, make sure the right to approve the cover is in your contract. Throw a diva fit if you have to. Don't let a muddy Poser cover happen to your book. Seriously. It's worth offering to pay for a decent cover out of your own pocket if you have to (but you shouldn't have to).
(Notice how I cunningly demonstrated that being able to post graphics here at E2 would be a right handy thing? Don't fear the JPEGs; we're not turning into Flickr.)