Can anyone clarify, what makes this art not relevant to the site:
https://e621.net/posts/4746268
https://www.furaffinity.net/view/11357371/

but for example, these are fine?
https://e621.net/posts/3085328
https://e621.net/posts/340381

You can send a message to the janitor in question, @Mairo, to ask why they removed your post.

Generally though, we don't accept zero_pictured content (by definition, "A post that does not have any characters, or likenesses to characters in it.") unless it accompanies a larger set that has furry characters.
In this case though, it does seem like there is a character in the card but it might have been missed.

thegreatwolfgang said:
You can send a message to the janitor in question, @Mairo, to ask why they removed your post.

Mairo doesn't respond to messages unfortunately, so in this case @NotMeNotYou should be contacted instead.