macOS changing wallpaper
Changing the wallpaper on macOS is really easy from CLI using Open Scripting Architecture (OSA) and its tool osascript:
$ osascript -e 'tell application "System Events" to set picture of every desktop to ("~/Pictures/wallpapers/cool_wallpaper.jpg" as POSIX file as alias)'
Same thing using JavaScript for Automation (JXA). Save the code below to a file named change_wallpaper.js for example.
var system_events = Application('System Events');
for (desktop_item in system_events.desktops) {
system_events.desktops[desktop_item].picture = '~/Pictures/wallpapers/cool_wallpaper.jpg';
}
Run it like this:
$ osascript -l JavaScript change_wallpaper.js