It might be ancient at this point on internet time, but the G4 movie was a huge undertaking if we really step back and look at it. The amount of hands that went into making it is pretty massive.
Another artist has posted up a gallery of all of the art they did for the project, including cut characters and background elements we never even got to see! Including stuff that wasn't in the movie book.
Check out their full gallery over here.
Thanks to Dakota for the heads up!