Cicada

I once saw a foot long stick insect in Byron Bay a few years back, sore I didn't take a photo now!

I think you mean the largest in the spittle bug and tree hopper family. Some of the largest insects are moths, beetles, katydids, and walkingsticks.

I remember from mythbusters Cicadas are one of the largest insects ever.

That looks like a leaf, something i'm only used to seeing with Katydids, walking sticks, or praying mantids!