I don't think you can. Plus, I think (and hope, in a sense) that Google is trying to "keep it simple".
i see here http://talkgadget.google.com/talkgadget/popout sign in then click your friend id then see the bottom right cornor but i want to add in G-talk... now help me
I believe that you can only use emoticons in goolge talk: http://mail.google.com/support/bin/answer.py?answer=34056
you need to install another smiles program on your PC then you can add funny and animated smiles on your gtalk