I have problems with paranoia, which can sometimes be set off by pictures of distorted faces and eyes.
Unfortunately those things are a staple of horror games now a days, which are very popular in indie games.
While I have ways to circumvent looking at the popular/recommend sections for my own comfort, I was wondering if there is a way to filter or blur the thumbnail images of games tagged a certain way to avoid seeing something that could be triggering.

I glanced through the settings and saw nothing about blocking or putting a warning on certain tags in the content section.

As explained in lots and lots of topics, there's a hidden feature. Since people often want more, one of our members made a browser extension too.

I'll have to fiddle around with the browser extension, thank you for the quick response.
I apologize for not looking more thoroughly, as after seeing the hidden feature mentioned it didn't occur to me to look for a 3rd party option.

Tough. If it is horror games in particular you want to not see, that is trivial. Use a bookmark to access your favorite searches.

https://itch.io/games/genre-rpg/tag-pixel-art?exclude=tg.horror

If it is all thumbnails you want to blur, that is kinda trivial too.

@-moz-document url-prefix("https://itch.io/games") {
    
    .game_cell img{filter: blur(7px)}
    .game_cell img:hover{filter: blur(0px)}
}

Put this into a user style extension as a style. It will blur all thumbnails, until you move your mouse over them.

Preemptively blurring/filtering tags is a problem, since the tags are not displayed on the page in most cases. (Main) Genres are possible.

But blurring is probably not helpful. It might create new simulacrum images, so you would see faces, where there are none.

@-moz-document url-prefix("https://itch.io/games") {
    
    .game_cell img{rotate:180deg}
    .game_cell img:hover{rotate:0deg}
   
}

Maybe another image transformation might help, like {scale: 0.3}

If you are just bothered by the images but can stand selecting them, so you do not see the game next time you browse, I suggest looking into the third tool on that project page linked above. You just press a key with the mouse over a game and it will disappear. For filtering I consider it far superior to tag exlucions.

Tags are unreliable. If you filter out horror, your still get psychological horror where there might be more distored images and you cannot be sure if developers tagged both.