Home computer - Death Star trench run
Work computer - Tron light cycles
Phone - My 14 year old beagle, Ginger, wants some popcorn
Phone is my cat
Home puter is just black.
Work puter is stupid corporate crap that came with the image.
Home and work desktop machines - original XP Azul wallpaper
Phone - HTC Middle Earth (my name for it) wallpaper
Tablet - Starfleet LCARS wallpaper
Interesting. That’s one of my watch faces.
Cats, cats and more cats.
Work: I change it every week, usually something thematic to amuse students (e.g.).
Home: My lovely wife.
Phone: Cats.
Ipad: Penguins.
My laptop has a picture of a cloudy sky at sunset that my son took when he was about 8 years old or so.
My phone has a photo of the Golden Gate Bridge that I took as we sailed beneath it on e cruise a couple years ago.
Phone - a picture of my dog George
Tablet - a different picture of my dog George
Laptop - a picture of my son playing fiddle, from behind with his very long hair and a very cool design on the back of his shirt, the picture has be stylized to look like a painting.
My phone just has some generic green design. Anything else just interferes and distracts me.
My PC changes regularly, I usually make them myself with image I like, which I convert to the right aspect ratio and resolution. It currently is a carousel of over a hundred images featuring pretty celebrities, mostly pro photoshoots but wearing casual clothing, very little implied nudey stuff. Here are some safe-for-work samples.
On my laptop i have a family potrait and on my phone i have a snapshot of my grandson taken at his birthday party last year for the lock screen and a snapshot of my grand daughter on the main screen
Work computers: standard Windows logo.
Phone: default Firefox BG.
Home computer: monochrome black (and no desktop icons either – I use a tiling WM).
For some reason, that wallpaper thing has lost its novelty for me long ago.
I cycle through a set of pictures from the Juno mission. Currentlythis oneon all screens
Home and work computers - pictures of my granddaughter, because that’s what grandmothers do.
Cheapie flip phone - a fire in our pellet stove - I was trying out the camera when I bought the phone.
Tablet - whatever the default was - I never changed it.
Here at work, my wallpaper is a pic of the house on Anna Maria Island where we vacation each year.
Eight and a half weeks away, but who’s counting? 
My default wallpaper for everything is a pic I took of a mount of personal significance.
One thing that bothered me about using it everywhere is that my e-reader falls back to it and keeps it there as it hibernates/turns off. So it took a while to get used to seeing something like this on a screen for a device that is “off”. E-ink is da bomb.
My phone keeps wanting to rotate the background depending on phone orientation. No! If I gen’ed an image of exactly right size to fit the background, why are you rotating it???
Phone - Dark purplish lake sunset. Enough for some color pop, but dark enough so white icon lettering is clearly visible.
Tablet - Spashy stock colors that differentiate users.
Computer - Solid black
Phones - whatever the default is
iPads - whatever the default is
Computers -apparently, what is called “solid gray pro ultra dark.” Basically, just a solid, dark gray. I do a lot of photo editing, so I don’t want anything distracting in the background.
I used to change wallpapers and lock screens, but now I mainly stick with the defaults. My laptop though is showing the global cloud density map that made the rounds a few years back: http://www.abc.net.au/science/articles/2015/05/12/4233502.htm
That might just be windows 10 now remembering settings on my microsoft account though.
Home is this Chicago skyline image
Phone is some stock “black with a dark blue wave” image
Work is default Win7 wallpaper.
Phone is a picture of my kids from this past winter. I need to get a new one, I know.
Home computer is a rotating slide show of snowflakes. Yes, it’s June. I love snowflakes and won’t be changing that one any time soon.
Work computer is a rotating slide show of various waterfalls.