macOS Big Sur: how to change background and icon size in login screen?

Good idea ! BUT with : Latest Onyx version [ 3.9.3(2012231) ] and MacOS Big Sur 11.1 I'm unable change the Login Wallpaper.

The reason is : The option to do that is no more present in the Onyx tools !

Too bad - we are forced to wait from Apple to change this situation or from Onyx to find a solution to restore this functionality.

Sorry it didn't work for you, it worked for pretty much anyone who tried it on here.

If it didn't for you you likely have FileVault active, Guest account active, or a multiple user config.

The instructions are all correct...but they only work if you have a 1 user setup on your computer.

The icon size problem is so strange because they made it huge but didn't update the default selection of images to make them higher resolution, so they all look awful... has anyone figured out how to change the size of the icon yet?

When I boot my MacBook Pro, it has the default background and one of the two external monitors has it as well, the other one has the one I want.

Then I set again the same background on each 3 screens, but this is not retained at all. At each boot, the built-in screen as well as the HDMI monitor revert back to the default Big Sur background. If I disconnect the external monitor, the buil-in one reverts back too.

So it doesn't seem to be related to the configuration.

Besides the 2nd monitor retained its custom background image.

I won't turn FileVault off just for this! It's non-sense !

Obviously it is a bug. I never had that problem on my former MacBook with the same configurations and devices connected.

Not to be annoying here, but I have a new MBP 16-inch, I am the only user, File vault off, Guest user off, read & write permissions granted.

But still the ugly login screen. Most frustrating part of this is how frustrated I am about allowing my self to get frustrated over this stupid screen..... but feels like a mission now.

Appreciate your effor for the fix, and glad it worked for some.... would love for it to work for me.

And have you managed to change the icon size? Because now login screen icon size so big. I thought some settings were set in "Accessibility Options..." - but not ... Maybe you know how to change it to normal size?

Just figured it out: right click anywhere on the screen. Choose "chamge desktop background". There is quit a lot of new ones.

I don't think you got the sense of the question

I've tried to fix this for myself as well, have found nothing so far...nothing at all.

Well,

Each time I reboot, the standard picture is set back to the background. Very upsetting.

Ah too bad. The single user rule wasn't in the instructions because at the time I think nobody (included the person who came up with this method-not me) was aware of this but now it's 100% clear at this point.

You can wait for OnyX to be released for Big Sur then you'll be able to customise the login wallpaper in just 1 click. It's a free software: https://www.titanium-software.fr/en/bigsur.html

I agree, My wife agrees & is Upset about this hideous Screen Color & Icon Size & our Giant names splashed under each icon photo we used before this great "upgrade". Computer Fools Just Trying to justify their jobs & corporate existence: Hey, You Geeks SMARTER than the REST of The World: Just UPGRADE SECURITY & leave the rest of us alone.