This looks like leaves. I am not sure what I am missing.
When I look at it, the very first thing I see is the sharply-delineated fuzzy region at the left. It looks as if it is something rather than (as it were) mere blurriness in the gaps between other things. There isn't any specific wrong thing my brain wants to think of the image as showing, but when I first looked at it it took something like half a second to figure out what I was looking at.
I'm not sure I'd call it almost like an optical illusion, though.
Would you say the picture below (by A. S. Shevchenko) is almost like an optical illusion?
Have you seen any pictures or sights that fooled your brain for a moment but that you wouldn't call optical illusions, and if yes, what is the salient difference?