Why not OMNISEX? That should cover them all.
Or they could put a big poster on the door or an outside stand that says, "LGBTQxyz Toilet" with the xyz in pencil. If more weirdos pop up, just add more Sharpie letters as in, I for incest love; B for beasty love; P for poly-amorous love; R for unconscious rape love (she asked for it); H for hidden love of burka clad. Oops, forgot D for disgusting breeders. How about M for masturbating? S for sneaking a peek? Any perv I'm missing?
So, for now it's LGBTQIBPRHDMS. Phonetically pronounced, lug-bu-tqui-be-friends-dumbs. Can't wait to see the morning shows.