I want to report my manager for overdoing holiday decorations in the cubicle space
Why do the decorations bother you that much?
I cannot concentrate on my work
You are behaving in a very petty way. You are being a scrooge and a grouch. If something bothers you, it is best to speak directly to your manager instead of reporting him for something so petty.
If a fucking Christmas garland over my desk is a problem, then we have a major problem.
You should just ignore it and try to get into the Christmas spirit. It is only a few weeks out of the year, just try to be more understanding.