This has been done before, but the threads I turned up with searches are a couple years old, and these things change. So let’s do this poll again.
I change mine fairly frequently. Right now it is a picture I took at sunrise in Ocean City, New Jersey. (On the beach, looking through that old decaying pier thing near 59th Street, for those who may be familiar with the place)
Background is a nice plug for Opera. Blue, with the Opera “O” in the bottom right corner, some guy with a telescope in the bottom left and, next to the “O”, a plug for www.opera.com beneath the words “Simply the Best Internet Experience”.
Love my Opera browser.
The scoreboard at Fenway Park.
Right now, it’s a gorgeous shot of the Neptune Pool at Hearst Castle that I downloaded from this site.
Repeating pictures of orlando bloom, colin farrell, brad pitt and johnny depp. I like my wall paper!
An image from the Hubble telescope
A picture of a county road in northern Idaho; my dad surveyed the road one summer when he was in college.
(part of) a movie poster for the 1932 version of The Mummy, showing Boris Karloff’s head and the slogan:
“And now KARLOFF the uncanny as ‘The MUMMY’ - it comes to life!”
Right now it’s Alice from Dilbert saying, “Must…control…fist…of…death…”
One of my co-workers gave it to me. He said it reminded him of me for some strange reason. 
I made mine in photoshop from a picture I found online of a water droplet hitting a pool. Here it is.
Likewise. Specifically, Recycling Cassiopeia A
Just the other day i found a good painting for my desktop…
it’s called Idyll, and it’s by Lord Frederick Leighton.
I am so boring. I have the compaq palaver the computer came with. I have just never been inspired to change it.
The child changes his on a near daily basis though. I think it is currently a Neopet. We have the same computer just different users, that was his idea.
A picture I took of the N R(?) platform at Times Square station 2 years ago. It was about 4:30a, so the platform and station were empty.
A photograph of Pont Neuf in Paris.
At work its a picture of Havasupai falls from last years trek there.
At home it WAS Madonna until my husband started poking around and made it INXS.
I dont mess with his computer, why does he mess with mine?
I rotate between the more artsy (sunsets, wildlife, that kind of thing) of the photographs I take at work.
Like GorillaMan and OttoDaFe, an image from the Hubble telescope (the Orion Nebula, to be specific).
We’re such geeks 
I belive that it was this sort of thread that caused the abandonment of the [img] tag.
Naked Sable playboy pic.
[Homer Simpson]mmmmm, Naked Sable…[/Homer Simpson]
