>>8362
Personally, I feel that for OP images ESPECIALLY, it's very important from a board quality perspective that the image that starts the thread is on-topic with the board's subject matter. The OP image is the "Cover" of the thread to me. When I view the Gallery, it shows me a display of images. Take /vg/ for example, if I go on there right now, I see a wide variety of different items. Let's say I'm looking for a thread about Dragon Ball -- At a glance, I can see a thread with the OP image of Super Saiyan Blue Goku and immediately be clued in that that thread might be just what I'm looking for without having to read further into it.
Now imagine if the entire board was Pepes or Wojaks. Sure I can just dig around by reading the thread subjects, or typing "Dragon Ball" into search, but why should the cover of the Dragon Ball General thread be a completely unrelated frog? To a normal user this would be in my opinion a lower quality experience than if the thread OP was posted with an image relevant to the intended discussion.
Now, if someone is using a pepe or wojak in their reply within the thread? This is less impactful to the board's quality. In my opinion it's still lower quality than if the poster had used an on-topic image, but it's not that big of a deal since it isn't what will persist on the main page of the board for potentially days if the thread is slow enough.
The /vg/ example can be generally applied to most boards that have specific topics in mind. Imagine if someone posted a Madoka thread on /a/, or an Evangeleon thread on /w/, but instead of a related image they used a wojak. Definitely a stark contrast. But if they did the same thing on a more generalized board such as /b/, /g/ or /biz/ for example, well it's not like I'm looking for a particular theme when I look for threads on there anyhow, so it's less impactful on the board's quality.
These are just my thoughts on the subject as to why it might be different depending on the board.