I hate having to resort to a legend. I prefer to let the map speak for itself by coming up with visual solutions to problems like this one, but it's not always easy, or even possible.
As for this game, there are some items for which the sprite has a light outline and some that don't. I don't want to use an effect to represent a specific condition if that effect that's already there but *not* for said condition. Anyway, I'll think of something, hopefully.
Incidentally, World 2 is fully mapped. The maps look good, but so far they don't have the variety of 'Gimmick!' nor do they have well hidden secret areas. A bit too straightforward for my taste.