I agree, it sucks how you are unable to change the layout and various colors in the Vista and W7 logons. The XP logons did, indeed, rock. There were some VERY creative things there. Applying a background just doesn't cut it. Which is why I didn't buy logon vista, honestly.
My best guess would be that the design of the logons for Vista and W7 are somehow hardcoded by Microsoft to prevent modding or tampering. Which sucks, but is the only thing I can think of as to why you can't change all of it in LogonStudio.