Shoutbox

I now realise that it would only show on your own computer.

But,

You need something that would append the sig to the message before it was sent to the other contact. (It could contain plaintext, or have code in it for plus! users, but they would need plus! to view a formatted sig)

hm, why not use quick text? It wont be after EVERYTHING but you could use it at the end of your conversations. so "/bye" could be "au revoir my little friend!" or some crazy jiberish...and you could use the stuffpluf ng to make bigger emoticons so it could be like "/bye  = au revoir my little friend! *photo of you waving*" just a suggestion.