If I were standing on that white portion and needing to cross to one of the outer edges I'd say I was probably screwed. I get the 3d effect, it's like looking through a sheet of ice..or is it a series of holes....if they are confused then just tell them: "Well, you might be screwed", LOL.

To me it looks like looking down the fibers of a bone if it were clear like ice but I only really see it if I zoom in.

It is also possible that I see something entirely different from what is there as I tend to do that a lot. I think it's the artist in me.

As far as a map goes, if you can use this to keep track of where someone is then I'd say it's a map. If nobody else can read it, then it's a coded/secret map. How fun is it to hand the players a key to their problems only they can't figure it out quite yet. Of course, if in the end they still don't get it, you might have missed the mark.

I would also just add that on first look it just seems like an odd watercolor painting or something.