I use a slideshow of 8 or 10, uh, images starting from the Solar System and going by progressively more encompassing areas of space right up to the Observable Universe. I like keeping track of where I am.
BTW - did you know we’re just about right at the center of the Observable Universe? How weird is that?
Does that mean The Bible is right after all? 
I can’t link to it from work, but currently my home computer displays “OotS as Star Trek.” Rich has poster several cool wallpapers on the website for those of us who contributed to the Kickstarter campaign. OTOH, my school computer has this as the wallpaper.
Here’s one I took yesterday - it’s in the “wallpaper” rotation now.
This picture I took of my wife watching the sun set at Shenandoah Nat’l Park a few years ago.
Don’t have a place to post it online, but mine is a picture that I took of the Haleakala volcano crater on Maui.
Beautiful!
Currently a recent sunset in Brookings, Oregon.
I alternate between two shots of the main drop of the Micos Cascades, one that looks like this picture, and one that I took from the trees at the top.
Just some generic mountain/woods/lake picture that came on the computer. It might even be the default background, I don’t remember. It’s kinda purty, tho.
I use John’s Background Switcher, which can get images from various sources, such as flickr or Google Image searches. I have it set to get a new image of art or architectural ornamentation every day. Today I get to show off how cultured I am :). It’s Rubens - The Holy Family with Saint Elizabeth, Saint John, and a Dove.
I like to take macro photographs of flowers and insects, and have both my “wallpaper” and my screensaver randomly sample my collection.
I change my desktop wallpaper regularly, I have quite a bank of them set up in my settings, and swap them around whenever I’m in the mood, probably every two weeks or so. I usually make my own, which is to say I take somebody else’s photo or artwork and format it to fit my monitor, though occasionally I’ll get more creative and make it more elaborate.
Right now I have this, which all I did was resize.
One of my own, of Hadrian’s Wall.
Got a bit of a shock when I upgraded Windows 10. Its default theme colour turned out to be its idea of a dominant/toning colour to the photo, and it had decided on a particularly vile shade of duckpoo green.
I have a couple. On my desktop with a dual-monitor setup I have this panoramic view of Cape Town stretching across both screens. On my laptop I alternate between this coastal view and this spectacular railway scene.
My photography. About 10k images that change every 15 minutes.
Win7 has the world’s shittiest slideshow program, however. Out of 10k images, there are many repeats. I hope Win 10 is better.
Currently I’ve got this one up https://c2.staticflickr.com/6/5795/20259037764_bf183cdde5_b.jpg
Before that I had this APOD image up APOD: 2010 August 23 - A Milky Way Shadow at Loch Ard Gorge
I usually have video game screenshots (portraits of my characters, or really cool backgrounds, mostly). But right now, it’s the Peanutized Me.
I used to have a slideshow of Hubble telescope pics that would change every 15 minutes, but since the grandbaby came along, his little mug has taken over all of my picture space.
Win 7 user here and I have about 30 themes. Change the theme every day. Wish I could find something that would change the theme daily for me, but so far have not. Haven’t searched all that hard.
