The storm symbol looks like a lightning bolt. The life symbol looks like leaves. The fire symbol looks like flames. The balance symbol looks like a scale. The ice symbol possibly represents the stability and defensiveness of ice, or possibly a snowflake. The myth symbol looks like a pyramid with a cyclopic eye.
But what does the Death symbol mean? What aspect of the school does it represent? It doesn't really look like anything. The only thing I can think of that it might be a gravestone.
Opinions? Comments? Flashes of Inspiration? Post post post!
Edit: Yes, I mean the casting symbol, not the skull. Silly me.