Here's a thought. Mood comes down to style to some extent, so instead of pedantic descriptions, do more of a fragments of consciousness approach:
"elaborate patterns ... fading" of some old wallpaper.
"rough, and somehow comforting to touch" of a tree (specifically the bark where you touch).
"whoever lived here ... their personality feels still present." of the comfy chair in an old abandoned house.
In a given area, the incidental interactions can contribute to the general ambience or mood.
And you can still have humour that plays off the feel that you're trying to create.
For example, the character is alone, but feels watched, and so relieves the anxiety by acting as though someone else is there. "Oh, after you." stepping back from a door and gesturing before using it. "Anyone else for tea?" while making tea. That could be both funny and unsettling, as the player doesn't know it's coming, and has a moment of trying to figure out what just happened.
"elaborate patterns ... fading" of some old wallpaper.
"rough, and somehow comforting to touch" of a tree (specifically the bark where you touch).
"whoever lived here ... their personality feels still present." of the comfy chair in an old abandoned house.
In a given area, the incidental interactions can contribute to the general ambience or mood.
And you can still have humour that plays off the feel that you're trying to create.
For example, the character is alone, but feels watched, and so relieves the anxiety by acting as though someone else is there. "Oh, after you." stepping back from a door and gesturing before using it. "Anyone else for tea?" while making tea. That could be both funny and unsettling, as the player doesn't know it's coming, and has a moment of trying to figure out what just happened.