First, download a snow falling screen saver using the below link or find another online (other screen savers work too):
https://www.macupdate.com/app/mac/20033/lotsasnow
Next, set it as your screensaver in system preferences
Finally, use the below command in terminal to use it as your desktop background:
Code:
/System/Library/Frameworks/ScreenSaver.framework/Resources/ScreenSaverEngine.app/Contents/MacOS/ScreenSaverEngine -background
I think that it will reset every time you reboot or log out, so create a script and make it a login item like so:
1) Open "Automator" which is either in /Applications or /Applications/Utilities
2) Create a new application
3) In the side bar there are tons of items, scroll down until you find "run shell script" and drag it into the empty space on the window
4) Paste the command I mentioned earlier in this post into the text box where you dragged onto
5) Click run to make sure there are no errors
6) Save it to any location
7) Open System Preferences>Accounts>Login Items
8) Drag the application you just saved into the window.
9) Enjoy your snowy wallpaper/screensaver