The votes are in, and thanks to everyone who weighed in (including the handful of you who clearly enjoyed the thread more than the art itself). You voted almost 2:1 against leaving things as they were, but most of you didn't want a flat ban either. The clearest overall message in the discussion was that people want enforcement and guardrails, and that's the fairest outcome for both the artists and the people who just want grimdark in their feed.
We didn't want the rule to feel like it was targeting specific individuals in their taste either, and there are enough examples of "out there" art that people were irked by to create a fair catch-all for stuff that's not really in line with official depiction of the Sons of Nostramo.
So here's the new rule:
Art depicting Night Lords characters or Astartes as things other than what they are in canon lore (eg as anime/comic/other characters, animals, anthropomorphized objects, gender-swapped, etc.) or in situations that do not occur or are implied to occur in canon lore (eg tea parties, dance raves, etc.) must be tagged as "Fanon Art" and also marked NSFW if appropriate, which includes both excessive gore and sexual content. Failure to do so will result in removal, but you can always re-post with the right flair.
In plain terms, Curze in a maid outfit is fine, and so is Sevatar hosting a tea party, but tag it. Gundam Night Lords, your favourite anime waif in Midnight Clad. All fine. Just tag it. If it's spicy, mark it NSFW too. If it looks like something that is within GW's lore, it gets the regular "Art" flair. If it's official art, it obviously does too. Almost in response to the poll and discussion, this thread appeared. I've manually updated its flair as example.
We're not judging your art, and we want to reiterate that this subreddit wholly supports GW's official "Warhammer is for Everyone" position. The goals is to ensure people who scroll here on their lunch break know what they're about to open.
A removal under this rule isn't a strike against you. Fix the flair, re-post, and carry on. Anything that breaks other sub rules (or Reddit's) still gets pulled regardless of flair, and the usual expectations for comment sections have not changed.
The rule is in effect immediately. Reddit doesn't allow subs to re-order post flair, so it's at the bottom of the list.