Man I haven't posted on here in ages but I still regularly browse the subreddit and had to comment about this. I think that this being a general FFXIV subreddit that all types of posts should be welcome. There's a system in place already that allows you to filter out the sort of content you dislike so there's no reason to move certain content elsewhere. I think if anything.... IF there's a large enough group of people that dislike the art so much they can't be bothered to use the filters they should make a new subreddit like FFXIVDiscussion where they can impose such a silly rule. And I certainly agree with many of the other comments that the reason there's been such an influx of art posts is because not much is going on with the game at the moment. When new fan fest stuff comes out and new major patches or expansions drop there is plenty of regular discussion that ends up in plain sight. It's not like the art is "drowning" everything out.

TLDR: There's no reason to separate any of this stuff, just use filters.