It's amazing how many great fantasy artists there are. And when I go to their site, knowing only one or two book covers they've done it's fun to see how many OTHER covers they've done that I know.
Take Matt Stawicki as an example. I knew he'd done more of Carol Berg's covers, but I didn't realize he did Karen Lowachee's or a lot of the newer (and much better looking) Dragon Lance covers.
Cris Ortega is a Spanish artist who I discovered through her own book of stories and artwork, Forgotten. It's haunting but beautiful.
An artist whose covers (at least on Solaris titles) almost force people to pick up the books, Michael Komarck. When Summoner first came to the store I knew it would be a hit. With cover art that good, how could the book possibly be bad? (I know judging books by covers doesn't always work, but sometimes, as with Summoner, it does.)
Finally, an artist whose covers I remember from my teens, Keith Parkinson. He did the original covers for the Death Gate Cycle (Margaret Weis & Tracy Hickman), and writers like Terry Brooks, David Eddings, Terry Goodkind and more.