My custom injury systems was inspired by a computer game (which ironically, is the sequel of an adaption of a tabletop game that was inspired by D&D - Warhammer Quest 2). I had this coin-drop moment when I saw their injuries system was not full of permanent effects but instead temporary setbacks. You don’t lose a leg or get a permanent limp, you might just have broken or sprained it instead and it’ll heal at the end of the dungeon.
Beforehand I had been stuck in basing my injury systems off 90s wargames like Necromunda. You can see the same in the DMG where its suggested list of injuries are 90% permanent if you don’t have access to magical healing.
Making them temporary was the inspiration I needed to making the system fun - players don’t want to retire their character after they take an arrow to the knee, but if one of them has to be strapped to a sled and given a crossbow while you race across the tundra pursed by packs of winter wolves as you try to get back to town - well that’s an awesome experience.
I also like to design my dungeons like Zelda dungeons with a central chamber and a few branching routes. Having something that can alter the dungeon makeup too is a great twist - for example I have one where lighting oil braziers in rooms transforms that room into the past where the passage might not be blocked, but it is filled with the original denizens (or malign echoes of them) and they aren’t happy to see intruders, (there’s a computer game that does something similar). I’ve always wanted to do a dungeon with rising water levels like the Water Temple in Ocarina of Time, maybe one day.
I take a lot of abilities and special moves from Pokémon too. My players fought against a yeti that brought down a hailstorm mid-battle - that’s a Pokémon move lol. There are some pretty out-there moves in Pokémon, for example “Trick Room” flips the initiative order of the battle for 3 rounds - imagine a spell caster that could do that! Another called “Special Room” switches everyone’s defence and special defence stats around. Imagine a spell that flipped everyone’s Strength and Dex for a round!
Anyways, there is loads of little bits of inspiration to take from computer games in general and especially CRPGs.