go to user cp, then go to edit signature, in the little box where you write ur signature click on the little button that looks like a postcard with a picture of mountains on it, then you get the url of the picture and put it in, then save changes, and thats it.
Actually I don't remember it (I never played a Mario game until Mario Sunshine), so thanks for posting that. I'll be checking out some of the old school Mario games on the Virtual Console- anyone know where I should start?
that's actually just a cut version of SMB3. I just say that because of the character design. I don't really like the game though, it's not sharp enough with the controls.