I have 5 desktops and it doesn't make any sense that I have to go in to "Change Desktop Background" 5 times every time I want to change them. Is there a simple way to make them all change at once or make all desktops have the same background settings?
honestly, No, I did not find an easy way to change the background as you are referring to,
I do not have much desktop as you, but how often do you change your desktop backgorund ? it's really needed ?
The user Preference file com.apple.desktop.plist contains keys for the default desktop picture.
Use something like TextWrangler or Xcode to modify the data there.