I need Help With Custom Background Creations

So Hey its me MyGravestone And I adding Custom Back Grounds to the the game Mario kart Cross Link Here https://mkpc.malahieude.net/map.php?mid=3193

For all the tracks
I will give you credit I have been making some to Btw But I don't Have ideas for any of them

i can give a few ideas for the nitro backgrounds

Gusty Gulch - a nighttime sandstorm
Piranha Shores - A Sunset Beach background
Baby Park- toys
Thwomp Ruins - Sand hills and a Thwomp Sphinx
Sherbet Land- Ice Crystals
SNES Mario Circuit 4 - Peach's Castle with a bunch of tress