Few ideas for planets, just for the heck of it:
A station that's the shape of a ring that surrounds a jump portal. Like they're studying it, but also providing ship support. You hit J to jump, C to contact them to land like normal. Maybe they produce products and buy products that aren't normally bought and sold at high volumes.
A hidden retro planet nestled in an asteroid field, just a bit away from a beacon. Tends to swarm with retro encounters. If you manage to wipe out retro encounters, or pirates or confeds take over, that counts as destroying the retro "fleet". So their faction would be a game-wide increase in retro encounters, and taking this out would reset their encounters to a low level until they rebuild.
A planet that is building or rebuilding a major city, so they always accept pre fabs, construction, computers, communications, advanced fuels, etc, but at decreasing rates, as in their economy becomes saturated and maybe changes to accept other things as it gets richer. Would be really cool if industries developed over time depending on what trade they got, but I think all my economic wishes should be focused into my own projects, since I seem to want to make an economic simulator more than blow stuff up half the time
A star that slowly degrades shields when you're in its coronoa. There's a base there that gives you high prices on a lot of things, but you need a strongly shielded ship to be able to fly there.
A terminal on one planet that accepts slaves for free so they can be rehabilitated, in exchange for increasing their faction rating, which lets you carry slaves without being attacked by authorities. Some people could use this to abuse the good will of the faction in order to trade in human beings, while others will use it to start to get missions from the faction on that world to free others through boarding actions.
A few planets that are hideouts for pirates, Kilrathi, retros, etc allowing for shootouts on a planetary surface. Might use the "can't see stuff unless standing there" tiles to obscure targets hiding in corridors. Maybe mission based, part of a faction that focuses on ground combat. You could also run illegal goods to these locations if your faction standing with pirates, say, is decent. They could also be inhabited by Confeds or Militia if the system they're in is currently occupied by enemy factions.
A Stock Exchange terminal where shares in commodities can be bought and sold based on the net indexes of all legal planets. Enemy faction takeovers cut that planet out of the market, which means prices can drop or go up due to warfare.
A wrecked spaceship, similar to the casino ship, where some of these weird terminals can exist, along with an eclectic group of pirates, Kilrathi, militia etc, all exiles and rebels with no other place to call their own. Offers unique services, even minor gambling, but can be blown up. If it is, you get faction bumps from many factions at the loss of all those services.
Debris fields, which yield space salvage, advanced fuels, and other random goods if you mine them like asteroids.
Mine fields that explode like dumbfire missiles if you run into them, with a chance for AI ships to also set them off.
Anyway, hope that stimulated some imaginations, at least.