Sankaku Channel/3D in channel

I'm not sure if these are actually allowed, but I've been finding 3D cosplays in the channel and not in Idol. An example would be entering ciel_phantomhive as the tag and finding a lot of 3D cosplay posts there. Is there any post that lists what should appear where (like rules) or these 3D I'm seeing something that shouldn't be there?

This is a borderline area at present - photographs of people should generally go in Idol, but we are not forbidding it or actively removing any existing posts.