Well, if you want to make viewer more funny, it has to be done mainly by the things which are available now. I suppose that developers doesnt wish to uncover the stamina effect like this to us.
Therefore happy/sad faces could be applied only isntead Xs and Os only. This thing could be made as a new option, like if you are changing skin of the site, you could also change the skin of the viewer and there could be available faces of the alliens or serious tough guys faces and so on.
Also there was idea of changing the commentary into more cool stuff. So with the viewer skin there could come something like a special skin language, so if there would be a robots, it would look like:
"Jump shot from far distance iniciated"
"Access denied"
And sad robot face. The actual emotions of player holding a ball could be in the corner of the screen as well as spectators which could do mexican waves and so on. It could be really funny.