Please have a look at this thread;
https://www.gametracker.com/games/minecraft/forum.php?thread=132163

It appears that a map image advertising a particular server has been allowed in.
The thread creator was told to load his own image, which appeared to gain immediate approval.

However, it seems from the latest post, that the old image (advertising a server) comes back occasionally, or is being overridden by another image upload.

I have seen both images myself, though only the legal one today.