The Meaning of Life, the Universe, and Everything.
This is a suggestion as well as a question, so I'll start it off with the latter.
First, while playing Minecraft lately, I swear I keep hearing a distant roar or loud bellow in the background (usually around every 45-60 minutes). I play with Turtle Beaches, and with music and sound effects on, so if anybody else is hearing this can you confirm it? If you have played Skyrim, it sounds really similar to the Silt Strider's bellow in the Dragonborn DLC or somewhat like a distant dragon.
Secondly, (just in case I am just hearing things LOL) I think it would be an interesting idea to add more ambient noises like bugs, wind, waves, cave rumbles, and birds to the game. Not at all times, because hearing crickets chirping for 10 minutes straight would drive anyone mad, but just in certain biomes or at night would add more effects to the game. I would enjoy being out on the deck of my house near the ocean waves, crickets chirping, and the occasional seagull fly by, it would really be an immersive feature.