All you've got to do to participate is salvage an old avatar or signature, or perhaps just do a general throwback and use an avatar/signature from an actual Final Fantasy game.

It'll be good for us to get back to our roots, because I personally haven't played a Final Fantasy game in quite a while, but I just started playing FFVII again and have become absorbed in it. I'm going to change my theme stuff in a few minutes, once I find the images I want.