Default Desktop for new users

Greetings!
For the last few years we’ve been deploying a custom spin of Xubuntu to our students that we were able to customize and lockdown. We’re looking to move over to the MATE desktop, but are having trouble figuring out how to create our “default desktop” (wallpaper, panel configuration, desktop locks, etc.)

I know in XFCE world, we could change a few XML files in /etc/XDG/… and all new users created would build the profile using those tweaked configs. I’ve tried to edit some of the Ubuntu-Mate override files in the /usr/share/glib-2.0/schemas/ directory, but new profiles still resort back to the stock Ubuntu-Mate configuration.

If anyone can give me some guidance as where to look, it would be greatly appreciated!

~ Aaron