Great job! This is exactly what I was missing in the game.
The only problem I see is the map colors are quite pale (more like the 2nd screenshot than the 3rd). And it makes it a bit difficult to tell apart hills, mountains and deserts. I think the color palette from EU4 would be better. Red-brown for mountains, brown for hills. It doesn't need to look good, just give information very quickly.

Really cool mod

Can confirm, works now.

The bug has been fixed, let me know if you run into any issues. You should be able to see the colored terrain in the main menu.

I realise there's a bug with it having 2 descriptor.mod files, I will try fixing it in a few hours