There are no apron items ingame as far as I know, and seen or found no specialmade here on CotH. But I know that some NPCs have aprons and would love to see the GMs design one. Perhaps two different ones, one filthy/dirty and a clean one? The best-looking apron I have seen so far ingame is the front half of a tabard.
Please provide which NPCs you've seen aprons on. That's a pertinent piece of information we need!
I looked through a few NPC's and I didn't find much apron wise.
This guy has some nice duds I would love to where though and it is sort of apron-ish. More trench coat, though.
You might be thinking of the outfit seen on Blood Elf Pilgrims, which is now made part of the thanksgiving stuff. I dunno if it's in our database, though.
Okay I will track it down, seen it rather recently so must be in Northrend or perhaps Myst Isles, but I will track em down.