imagine no enemies at all, with creepy music that also makes the planet feel empty, planet background would have alot of shades of grey, and not much color, and dirt would not be fertile,trees would be dead ones imagine records about an alien species or a big monster or something more sinister where the writer always types something like "its coming" or "what its that in the wind-(something happened and stopped writing/typing/idunno)" those planets would have really good loot but very scarce, encouraging players to explore the underground and the surface, slowly revealing what secrets that planet has and finally a boss summoner for whatever creature/creatures lurked in that planet located in a high security container an example on how the music could sound like or this
Most of the common monsters you see in starbound are brightly colored and make little "rawr" noises. The idea behind this is that something came to the planet and wiped out the seemingly empty civilization of all lifeforms. It wasn't meant to be that the planet is completely peaceful.
Perhaps rather than monsters we could have gigantic frightening aliens roaming the planet, (I'm thinking War of the Worlds style) that could be so strong you would either have to hide or bring a friend (imagine immense black tripods roaming the lands, burning any living creature with a heat-ray and scream "Ula! Ula! Ula!"
i just would like some horror in this game, i know that is not how the game is supposed to look in the end , but hell, monsters are way too colorful, even real life creatures look deadlier/scarier and whoever wants to say that pixels and horror don't go well then that person can shut up just google pixel horror games
or Mosters comming out at night from everywhere... Crazy doctors on the abandoned base, etc. So much you can do in this game. A bit gore/scary could be nice. Probably better as a mod.