I have a lot of ideas when it comes to worldbuilding. I have always been a fan of science fantasy (combining both tropes from sci-fi and fantasy), but I feel like most works haven't embraced both genres to their fullest potential. The original Phantasy Star series is probably the closest because they weren't afraid to actually call magic "magic" instead of "the force" like in Star Wars.
I plan on using these ideas for my dream game (or series), but I'm posting these worldbuilding concepts anyway just in case I never get to creating the game, and I just don't care if other people use these ideas. They most likely have already been done before (in fact I know some of these ideas have been done before). I'm using AI to generate these concepts because I suck at drawing.
Anyway let's begin. First off, I think alien worlds should combine both ancient technology, futuristic technology, and everything in between. Technological progress isn't a linear path, so you shouldn't assume that aliens go through the same technological progression as we do. They might be flying interstellar ships, but they might also still be wielding swords and bows. So you can have spaceships flying over medieval style villages or even mudhuts. Star Wars has basically already popularized this, so this should be a no-brainer, but you can always take it a step further. For example, replace lightsabers with steel swords while still having space travel.
This goes with what I said earlier, every gamedev community (outside of /agdg/ threads) is pozzed. You will be ostracized unless you fully subscribe to SJW ideology. It's why even in the indie scene, it's hard to find non-pozzed game developers. You even have to request an account (while providing links to other sites and profiles for manual approval) just to be on this instance.
So I thought of a fictional currency for an alien species where the "money" is actual a form of energy that is stored in the body and can be transferred from one body to another. From a video game design stand-point, it's brilliant because it's an in-universe explain on how the characters are able to carry that much money.
Something that I have noticed when it comes to science fantasy is that is is mostly combining medieval fantasy with space travel or steampunk with space travel. I'm all for a space wuxia or at least an alien civilization that resembles Ancient China or Asia in general.
Speaking of caves, I was thinking about having an alien race that builds everything in hollowed out caves, maybe in cliff-sides (like the Puebloans), or in completely underground caves. They probably might even hollow out asteroids, moons, and dwarf planets to make space stations. So imagine going inside a cave and seeing apartments, hotel rooms, restaurants, stores, etc.
Now for something weird. I have always had dreams of finding stores and restaurants in weird places. In my dream game, I plan on having the in-game stores be corner stores or convenient stores, much like in Earthbound or Pokemon, but given the schizo tech in this science-fantasy universe, you would have basically modernized convenient stores in medieval, old-western, or even pre-historic styled buildings. So there will basically be rustic, wooden buildings with modern beverage fridges inside. You can even have a cave with one room of the cave being a modernized convenience store.
So basically just have old-style buildings with modern (or futuristic) appliances in them.
Star Wars popularized wizards in space. I think we should also have witches in space. We can have alien witches flying between planets on their broom sticks.