Some fictional wonders:
Roswell Crashsite: 2 or 3 tile 'Natural' Wonder (ship and debris field). Unsure what the benefits would be, but it definitely would be science based.

Darvaza Gas Crater - eternal fire

Seconding Santo Angel. A tall and narrow waterfall like Angel Falls would be great, since wide waterfalls Niagra and Victoria are both hard to represent well in Civ graphics. The fact that Angel Falls is on a tepui is even better, as there aren't any other jungle-topped mountains in Civ (OK, Mount Rorairma is in the base game but the graphics make it just look like a grassy plateau). This kind of landscape where you end up with "islands" of rainforest on the top of steep cliffs is super cool - the landscapes of Viñales Valley in Cuba could also be a good one.

There are no tundra-bias wonders in the game either, so I'd love to see an iconic glacier like Vatnajokull that could add some benefits to mountains or polar regions.

Darvaza Gas Crater sounds interesting for the late game. Re: aurora borealis, it's already in the game as a side effect of the solar flares in Apocalypse Mode.

Question: Can I borrow some of the natural wonders for my South America after Independence Mod?

And I have some suggestions that I could use myself!

Amazon's meeting of waters
Angel Falls
Iguazu Falls
(is it possible to model falls!?)
Aconcagua Peak
Colca Canyon
Río de la Plata
Titicaca Lake

I suggest a few "Natural Wonders"
1) Reynisfjara Beach
2) National Reserve "White Sands"
3) Iguazu Falls
4) Angel
5) Milford
6) Belovezhskaya Pushcha
7) Eisriesenwelt
8) Baikal

A few ideas to represent the large swath of currently wonderless land that is Canada:

- Bay of Fundy: A very large area of tidal flooding. Could be a tile that alternates between land and water, although that ability sounds like a headache to program.
- Niagara Falls: Because who hasn't heard of Niagara Falls?
- Moraine Lake: An azure blue lake found in one of Canada's most famous national parks; Banff

PS: You've done amazing work so far. I look forward to any mod releases & updates you might have going forward!