That's one of the secret animal screens. And in the screenshot, you are very close to the passage.
Aha! Now the funny thing is that, between when I left that comment and when you replied, I left the KS window running MP open, minimised & muted, and in the interim I've messed with a couple of other levels -- play-testing my own, and checking out the just-released "Underground" and "A Knytt In Time, League of Crap Players Edition" -- and, apparently, KS did that thing where sometimes it decides that you didn't really mean to minimise that window, and moves Juni in both games.
And I actually hadn't saved at the nearest savepoint (or I did, but did a lot of blind moving around!) and so, when I brought MP back up just now, I had to backtrack a goodly ways, from the beige-crosshatched area in fact, to get back to the screenshot-screen. Wouldn't you know it,
when I jumped across to the point where Juni was in the screenshot, I noticed that the glow started up halfway across the jump, which gave me all the pointing in the right direction I needed. How I never noticed that before... well, actually, I think before I wasn't jumping from the same place, so I wouldn't necessarily have seen it.
Very clever, putting it n the ceiling! I don't think I remember any other ceiling entrance passages... possibly I've missed out on more than just one secret area that way?
I'm quite fond of the visual effect in that area, all that green in those particular shades, and the little green turtles (which are my favourites of all the turtles in KS) matching so well. It is one of the areas where the music creates a feeling of... hm, apprehension? which, while not entirely inappropriate, does tend to keep me focussed enough on "okay, don't die here" that I can't quite appreciate those visuals as much as I might otherwise. Most of the areas where the music has that effect are significantly less green, also... I think the only other really extra-attractive green area where the music doesn't contribute to the "relaaax and enjoooy the soooothing greeeen" is where the beavers are -- coincidentally another of my favourite areas, probably in my top three for the level, largely for those gorgeous ferns, though the way the background tiles suggest an ambient glow helps with that as well.
And I'm also fond of all the little -- as you dubbed them -- secret animal screens. The animals' dialogue is so cheerful, and often conspiratorial ("have you...?"); those screens are absolutely essential to the charm of MP for me.