DON'T EMOTE LIKE LANG LANG. People will laugh!!
In my opinion you shouldn't "add" emoting to your performance. It's an unnecessary and superficial distraction from the only thing that matters - the music. Consciously making faces is not likely to help you play better either because you have to focus a part of your attention on something that doesn't have anything to do with the music. You shouldn't show the audience how emotional the piece is by making faces, but rather by playing it really *** good.
I sense this clip will be much more helpful.
Facial (and body) expression is important, but forget Lang Lang if you dont want to look like a clown.This one is beautyful: