TLDR: a few or several city layers that are pasted upon a planet depending on their population amount and level of industry similar to
THISI would very much enjoy a feature or mod that would show lights on a planet depending on how populated and industrialized it is, having a visual representation of your progress would feel amazing and would give a real sense of accomplishment as you see great settlements rotate into the night.
Im not totally sure how it would be triggered in this game but it could be done by either layering different transparent pngs over each other or having different ones for each level. Ideally there would be a different design for each planet so that you dont get cities in the middle of an ocean but that would add a whole lot more work to the project.
I was thinking at level 9 and ten you would start to see trans-oceanic highways and possibly settlement starting to form in more extreme areas like said ocean. Not like Holy Terra kind of population but just little spots here and there.
If you have any ideas or comments i can add them here in an edit.