I mentioned in the comments below that the phrase "that big thing back there" has been a go-to for Jordan and me for years, and this painting by Angus McKie is usually what pops into my head.If you think about it, TBTBT is a useful device, especially when you consider that most of these paintings are generated to be covers for sci-fi novels. You've got one picture with which to depict an entire novel, so it helps if you can inject more than one narrative element into the mix (foreground and background). Also, TBTBT is often partially obscured by mist or distance, making it a good backdrop for the book's title. A lot of the art we're talking about is composed a little bottom-heavy for the same reason; look to the upper half of the painting for a starfield, a roiling sky over an otherworldly landscape, or, of course, a big thing back there.
This was not, to my knowledge, created as the cover of a novel, but it's another favorite of mine by Angus McKie, and another great TBTBT.[Edit: Actually, maybe it was the cover for something. There's an awful lot of empty sky at the top.]
