If it's a sticker from a set that is on the piece it's intended to be
stuck on, there's probably a catalog entry for it (or you can add it if not).
If it's a sticker from a set that's on a different piece than the one
the instructions say to stick it on, or if it's a custom sticker, then you
should list it as a custom item. Or just take the sticker off...
United Kingdom, England
USA, Pennsylvania
Luxembourg