So right before I turned in the final art for Field Trip to the Moon, I had an idea for an alternate cover. It featured the class and space station more, and the bus less. Basically I just really thought the station should look like it spins to make artificial gravity. The editor passed on it, which I agree with, but I still like the way it looks.
This sketch show an alternate cover design showing the kids departing a station that spins to make artificial gravity.
And this sketch shows what that station looked like from space. The scale of it is much more enormous than the station used on the title page of Field Trip to the Moon. See below.
This is the final art of the version used.