I'm sure I'm not the only one noticing this: even forgetting about all the purer fantastical worlds that are possible, there are lots of more familiar landscapes that don't come up so often in mainstream tabletop gaming - by which I mean roleplaying, wargaming and board gaming - despite many of them being used in high-profile literature and cinema.
Some examples are mud flats and intertidal zones, seafloors and lake or river beds, cliff faces, tower walls and skyscraper skins, high plains and long slopes, offshore platforms, plenum spaces behind false ceilings or floors, courtyards and stockades, tall grasslands and fields of crops - and parks, gardens and farms generally - exposed ridges or peaks, shifting dunes, asteroids inside and out, maybe even comets, and giant redwood forests.
Even aspects of light could be a kind of terrain, possibly other atmospheric factors too.
There are probably individual uses of most, and clearly good reasons why some are not so common, like equipment in the case of the seafloor. I'd also imagine many of us use some at least partly because of all this. But still, they do seem underplayed in general.