Known as Frill Jigoku (フリル地獄, literally, "Frill Hell") on Pixiv. This tag is for images with unholy emphasis on frills.
Here's some good qualifications for entry:
Ungodly amounts of frills.
Multiple layers of frills in the same general area, especially on large skirts.
Frills over multiple portions of an outfit. Frilled skirts are common and almost required, so having frills on gloves, thighhighs, hats, sleeves, shoes, pacemakers, etc. helps.
Inventive or uncommon use of frills.
Frills take up a noticable chunk of an image. It's hard to place a number on this one, but if frills take up half the image then that post is almost assuredly qualified. A more realistic expectation would be somewhere along 15%.
For characters that usually wear a lot of frills, the bar should be a little bit higher than normal.
