Hello 13HARAMBE37, how are you?
There are people who ignore this rule and still manage to get their islands published, I can’t deny that. But here we are talking about a specific case in which the Island is not allowed to be published due to a specific rule infraction, so I’m trying to help to solve it.
In fact, we can use the same example you bring to the conversation to make an extra suggestion for Spicymage’s thumbnail: as you can see in the link shared by 13HARAMBE37, something that most of those thumbnails have in common is that they exemplify very well what the Island is about, including in the image the game mode and the extras that define them from the others, like characters (TMNT) or special weapons, to name a few examples.
Maybe you could try by making it really clear that your Island is a realistic mode by using assets that are not as common in the more normal Fortnite modes and are more linked to the experiencie you want to publish.