I’m not totally opposed to a main non-perky ears tag, but I’m not enthused either, because of the name issue.
Especially if it’s supposed to also apply to non-ponies with different “default” ear positions. “Non-perky ears” would be bad for many even toed ungulated whose normal ear position is horizontal, and perked ears are elevated as well as more forward. It would also be confusing for all animals with naturally lop/hanging ears.
We could go with something like “non-standard ear position
” which is long and unwieldy and might never see use outside of automatic implications (and perhaps the occasional case where taggers cannot decide if the ears are back or floppy), or “expressive ears
” which is more concise but probably easy to get mixed up with anything a random tagger feels accentuates an expression, including ordinary standard/perky ear positions.
We could also go ahead and split “ears back” from “floppy ears” (making them mutually exclusive, or not, although I will personally ree every time someone comes to tag my ears, that I already tagged “ears back”, as “floppy ears” as well), and tackle a possible superset tag at a later time.