There has been videos (space X comes to mind) of them hitting the firmament. So we don't really know what exists beyond the firmament, yes there could be galaxies, but not the way NASA portrays them. I'm not saying I believe it, but I keep my mind open to possibilities that are out there not explained to us as we wish them to be.
Which is fine, the fact of having an open mind, however, you can purchase a fancy telescope and use it yourself, and you wouldn't see something that is much different from space, galaxies or other planets in the Solar system that has been shown by space agencies. Now, there could be manipulations on pictures about Mars and the Moon, that's for sure. So it wouldn't be a black and white thing.