If you are not caught up on Fringe, avoid the second part.
Firstly, the Fringe code has already been cracked. It was cracked before I started watching the bloody show. Of course, it was a pretty easy code: pictures stand for letters and there's only 26 of those in English, after all. But what gets me is not that Abrams put a one word coded message into each episode relating to that episode, but rather his obsession with Greek. Because two of those pictures have Greek letters on them (and Greek keeps showing up in the show, as does Latin - GO ASTRID! - I am not sure if it's because JJ things these languages are mystical or because they are the languages of the mystics...or something).
1. So, the Phi-frog, as he's known. I find the pictures interesting, because they've all got something strange about them, relating to Fringe science, which postulates the theory that the Phi must do that to the frog. Because you get the twins in the apple and the dragonfly wing on the flower and the smoke face (which is weird In And Of Itself). Phi has a number of intersting meanings (in it's capital form). It's most interesting is that it is the reciprocal of the golden ratio in math. The golden ratio is considered an irrational mathematical constant, but the capital Phi is the inverse of that. So it's the opposite of a constant. On a frog. I haven't figured this one out in my head beyond the fact that the symbol's creator probably didn't care about the finer problems of that statement.
2. The second letter appears on the leaf. Now, I've heard the theory that's it's just a triangle. If so, I think that's a comment on math/science within nature, or against nature. However, as a Delta, the capital is substituted for any change in science or engineering, even on a microscopic level. It also, amusingly, it's the symbol used to denote a gene deletion. On a leaf
. That can't be accident.( So, Peter, right? )