My Ideas for the current BeamNG could be better Sky Colors or Rain Effects on the Windshield Sky Colors like that: it would give the driving feeling much realistic when you drive in the evening. and rain effects would be nice... Also better clouds..i mean the ingame ones are not the nicest looking ones.
the sky is already pretty good as long as you have light rays on. and rain would be nice, but it's quite dificult to implement properly. you would either have to invent a system where you go around all of the maps and mark the places where puddles form, (or you have to do actual fluid simulations, which they definitely won't do if they want to keep sys reqs within nasa's budget.) then also make perhaps animated textures of raindrops beading and running down windscreens and body panels, which would be tricky (though not impossible) to implement.
Actually, when it comes to fluids, I wonder if it would be possible to make for example radiator fluid leak on the ground and make puddles the same way as tire marks are made. I've been thinking about it for quite a while now and I guess that would be a nice addition.
It would be nice, though if it ever gets added, it would most likely be made of multiple textures depending on the surface. And the texture size would increase as the fluid leaks more on the same spot. That would be pretty cool.
Sky color (or rather sun color) is part of my mod. The Scatter Sky (used when TOD is enabled in maps, otherwise a skybox would give you exactly what you want) is quite a fancy piece of art in BeamNG, in short terms it replicates how the lights colors wavelengths travel differently at any given angle of the sun on the sky, giving those redish colors at low angles. Its combined with a sun color gradient and the light rays and so on. Just to show you what it can look like you can have a look at this pic from one of my earlier mod version:
