Sadly, afaik, there are no official images of it. As Skua noted, it’s not exactly canon, but to my knowledge there isn’t actually anything that contradicts it. As such, I think most lore nerds take it as fact. Also because, as Skua said, it’s way more interesting for the Khajiit to have had a space program where they stood on each other’s shoulders than not.

Also, Bethesda has severely neglected the Argonians and Khajiit, so people take whatever Argonian or Khajiit lore they can get. I think they’re “too furry” for Bethesda or something.

Admittedly, a Black Marsh TES would be difficult to do without it being an Argonian-only spin-off because, iirc, Argonians violently eject anyone trying to enter the marsh.

Meanwhile, a game set in Elsweyr would require a lot of effort due to all the different skeletons and character models they’d have to create. They’d probably double or triple the number of character models simply due to all the different forms of Khajiit (there are 17 forms, ranging from having the appearance of a basic house cat to being almost identical to Mer (elves) or Men (Redguard, imperial, etc)), with significantly more work if they tried to make them all playable with full armor sets.