Depends on the game. Honestly, I usually have music off unless it makes sense for the setting. Like I play GTA with the radio yes, but I'll turn the music off in God of War. I know that it adds to the experience. Call me crazy, but music playing from the sky doesn't work for me.
If they're gonna be dark, they need to have a good reason. Admittedly, sometimes gore/violence/rape for the sake of gore/violence/rape is the point, but usually I prefer to have some kind of plot to go along with it.
Was browsing earlier and came across You must be registered for see element. and thought a Nun tag would be nice. Definitely a specific kink like mesugaki.
Replay gallery is a good feature to have, even if it's just static images. I typically use them has checklists to make sure I haven't missed any content, especially when there are branching storylines. Not having a checklist makes me paranoid that I missed a scene or something. :(