I got the ONEm today.
Is there any way to restore the default wallpaper?
One thing to add: I think it looks nice but I could not find the wallpaper after I changed the wallpaper.
The one way to restore it that i can think of, is by resetting the phone. Go into settings, about your phone, and then erase phone data. It will reset the phone to all of its factory settings. If you haven't added much to the phone, this may be a plausible action, but personally i don't know how long you will stick with the default wallpaper, so i don't know if it is worth the hassle.