A better fullscreen.
When you fall there's an animation and you don't go default position.
Some indication when you take damage and not just the line moving. First time I fell into the void I had no idea if I was going to die, lol.
Ramps, cylinders and spheres! That could help with more "realistic" places.
Maybe some particles when you're walking? Like barely noticable but a nice touch. Maybe clouds.

And that's basically it.

I just hope the Polytoria team stop beating around the bush and release the next Polytoria creator soon.

That would be cool!