I am sorry you do not like calling the decorative background picture on the desktop 'wallpaper' You do not indicate what you prefer it being called. I have always had Macs (I go back to the bad old days of OS8 and 9). As I am an artist most of my friends also have Macs. The only word I have ever heard it called is wallpaper although Apple seems to often refer to it as "screen background" which seems particularly unimaginative but practical. I did find the use of the word "wallpaper" in a download of wallpapers from the Apple site. You can find it here:
And googling "Wallpaper for Mac" brings up tens of thousands of results:
So it appears that wallpaper is a commonly used name for the background image on the Mac as it is on Windows and on Linux as well. It doesn't really concern me who used the term first as it has become a generic term these days and all three major desktop platforms have been guilty of being "inspired" by each other from time to time and so they should. Convergence of design and concepts is normal for every kind of device we buy. Just think of the confusion that we would face if every refrigerator manufacturer wanted to have their own special name for the icebox, or every car manufacturer wanted the steering wheel to be known by their own term for it. Same for such things that are common to computers such as desktop, window, folder, wallpaper, cursor, mouse, etc. Apple invented some of the names and other people invented the other names.
This is all irrelevant however to the question as to whether or not the Leopard and Snow Leopard background aurora images are real photographs or fakes and if real, what is the name of the source nebula.