Not about "this picture", but about the official existence of Caster Scathach.
The "Hilarious in Hindsight" pool is about the specific picture. If you want to add this pic in the pool, that means you think "this picture" is hilarious in hindsight so it really is about "this picture". Again, I don't think there's anything hilarious. This is just Scathach wearing Cu caster's clothes, sort of a cosplay. I do see your point since this is loosely a prediction that became reality, so in the end the real issue is that the pool is poorly named. I believe most pics in the pool would warrant a "wow, what a coincidence this became real" instead of "haha, it's funny this became real" type of deal. I'm no pool cleaner and certainly not for these type of pools which are biased and most often lacking explanation for the pic added, so if you truly want to add it there's no one stopping you. I was just here to provide an opinion.