If you haven't heard of Deviantart, you need to. Deviantart is a place where artists (and more rarely) writers can post their work and anyone can see it.
I've been surfing in and out of it for years and I'm just beginning to realize what a good tool it is for writers. In my case, I'm working on putting up an author webpage. I managed to find images that are very similar to some of my characters and I've gotten permission to use them on my website.
Permission from: http://villesgodgirl.deviantart.com/
Permission from: http://asaenath.deviantart.com/
Waiting on (and really hoping to hear from): http://skategirl.deviantart.com/
What I like most about this is that I'm able to use artwork that I think is suitable to represent my writing. Because of this, I also think it is a very good resource for people who are self publishing. Normally, a publisher is the one who chooses the cover, not you. That's why some books don't look at all like what's inside of the cover. If you self publish, you have a lot more control over what your book looks like. That's one of the big reasons why people self publish.
While I was at CAPAU, someone asked about where they could get images to use for self published books. Someone suggested stock images. While you can find stock images on Deviantart as well, you can also find talented artists who are willing to work on commission, sell their work, or give you permission in order to make a name for themselves.
Oh well, that's my tid-bit for today. I'm going to go decide which pieces I am going to use for my website! Go have fun kids: http://www.deviantart.com