Clouds that moves with the sun on Daycycle or without it, and they could be faster or slower too.
Edit: Ambient sounds, blockland lacks that, we all know that sounds for ambient gives more life to the game, and we could choose which sounds we want on the Environment settings, also they could get quieter if you get inside a closed build, like a house for example
Waves that you could change the level of it, like you could choose if you want a very calm sea or tsunamis.
Underwater effects, such as bubbles snd stuff.
Bloom effect, for example, your inside of a dark dave and you see an exit which is very bright and then it goes back to normal when you get out of the cave
Wind, you could change the direction and the force of it, and if it's too strong it could push you if you jump, also the emitters could be affected and it could have a wind ambient sound, oh and you could make it visible if for example your in the middle of the desert and you could see a sand wind