I play a lot of random city builders and enjoyed most of what’s already listed by others here.
Haven’t seen these ones mentioned yet (I think), but you could check out these to see if any tickle your fancy:
Modern:
Prehistoric:
Casual:
Fantasy:
Medieval:
Sci-fi:
I made a couple of mods and published them on Nexus, and with the donation programme actually made a little money from it, even though I didn’t expect anything. If you want to make money modding without completely shitting up the user experience you’re better off just shoving them on Nexus and maybe making a ko-fi or something.