macossystem-prefswallpaper
I have downloaded various "Dynamic Desktop" wallpapers online, put them into a directory, and added this directory to my Desktop & Screen Saver preference pane.
The problem is, it does not correctly the thumbnails. They all appear to be the "Mojave" wallpaper, while in reality they each are different pictures.
Open ~/Library/Safari/.
It is there, called Safari Desktop Picture.jpg (or whatever the extension is).
If you're on Lion, to get to Library folder you may open Finder, select Go from the top menu and hold ⌥ Option. The normally hidden Library menu will reveal itself in the folder list. Open it, and proceed to Safari subfolder.
If you're not on Lion or just prefer the quick way, open Finder, press ⇧ Shift + ⌘ Cmd + G to open directory prompt and paste ~/Library/Safari/:
You can use Mojave's dynamic wallpaper. macOS doesn't natively support animated GIFs as wallpapers.
However you can use this https://lifehacker.com/set-an-animated-gif-as-your-macs-wallpaper-1756859302 but at the cost of a shorter battery life for a wallpaper that you probably wouldn't see in action because you got windows all over.
Your case is more like needing a really thin phone(GIF) which you are gonna cover with a case(windows) anyways.
Best Answer
On Mojave the system doesn't generate correct thumbnails. The only workaround is to place the wallpaper into
/Library/Desktop Pictures/and place its thumbnail into/Library/Desktop Pictures/.thumbnails/folder. This requires administrator password and can only be performed from terminal.Thumbnail has to have same name as wallpaper. macOS Catalina can create correct thumbnail. Custom thumbnails are only supported for wallpapers inside
Desktop Picturesfolder.