Neither 'Report' or 'Flag' allow users to flag images that break website rules.
For example: This image is 3 humans and an elf; It's clearly 'human focused' and lacks literally anything furry. Yet it was approved.
So how do users flag it for another look-at? Because it's clearly against the 'No human focus' rule, given 3/4 of the contents are humans, and the other character is 'pointy-eared human':
https://e621.net/posts/4911705
And I apologize if there was a way to report it for breaking site rules. I really could not find a way to do so, so it may need to be made easier to see, if it exists at all.