I've found that any iOS update seems to reset the centering of the wallpaper as well. I have not found a good solution so far.
Gabe Shackney
Princeton Public Schools
@cnelson
We have this filed internally as PI-002777 (for our tracking) and have that closed out Third Party with Apple.
You can kind of anticipate the offset by making the wallpaper "wrong" from the beginning.
The wallpaper seems to be skewing 50% to the right after a restart so, when you make the wallpaper, have the center point be 50% to the left.
It'll look wrong on initial deployment, but it should look right after a restart. You'd want to test that on a handful of devices before pushing it out to them all, of course.
We have also found that it seems to happen less frequently when the wallpaper is set with Configurator 2, but that method requires touching every device as it doesn't do it via a push, it just directly sets it on the device.
If you have further questions on PI-002777, please get in touch with support either by giving us a call, sending an e-mail to support@jamf.com, or by using the My Support section of Jamf Nation.
Thanks!
Amanda Wulff
Jamf Support
@amanda.wulff
That's not really a fix. I shouldn't have to make something "wrong" in order for it to work "right".
The problem is I enforce my wallpaper every night, so it would still look "wrong" every day, just so it would look "right" after a random restart.
A feature should just work "right," or not be a feature at all.
There has to be a better way.
I would recommend providing feedback to Apple by visiting apple.com/feedback or by filing a radar. This is system behavior of iOS after restarts and unfortunately not a parameter that MDM can control at this time. Hopefully if enough people submit the feedback Apple can prioritize a fix in a future release!
Have you tried setting scheduling ongoing commands? If you go to smart mobile Device group, under automated management. you'll see a radio button with the label "Schedule Ongoing Commands". you can set it so that it sends a command daily at midnight to set the wallpaper. If the user restarts the device and the wallpaper is off centered, the automated management will set the wallpaper again at midnight fixing the problem. 
This is very frustrating and yet I am glad that I found this thread to know I am not the only one having the issue. 
It's mainly a cosmetic thing for me. I worked hard to get a pic with our school logo and it looks great UNTIL you restart...I use the command to update once a day but from a cosmetic standpoint if you restart your device you will spend the rest of the day looking at a skewed lock screen. Disappointing. Not saying its on JAMF just saying I am disappointed.
We are having the same issue with our MDM (Meraki). Setting up groups and having the wallpaper change 3 times a day seems to keep it tamed.
So, I spoke with our Apple specialist and he says what causes the wallpaper to be distorted when the iPad is restarted is the wallpaper is not created using the proper screen size and resolution. Anybody else see this?
I'd call bull on that answer. Because if it were the case, my 9.7" iPad Pros would look perfect every time, and only the older iPads would have the issue.
If there were a way for automated wallpaper to push when an iPad starts up, I would prefer it to any of the other stop gap measures we've come up.
Clearly it's an issue Apple is just not prepared to fix on their end.
I can set a wallpaper from an image, and delete the image, restart my phone, no issues. Pushing a wallpaper once should be a persistent thing in the same way.
May 2018 and it still seems to be happening. Anyone have a real solution? I have a fleet of iPads from 3rd, 4th, Air 2nd, 5th, and 6th generations.
