To change you avi, go to change settings & Profile (you'll see it on the top right part of your dev site, the 6th of the list that starts with "submit new deviation"). Once you are there, see to the left there's a menu, the first option is identity... there is where you can change you avi...
I'm not sure what you mean with smileys, if you mean emots like this ->
while you are writing a comment, there's a link to the emot list every time you make a comment on the bottom right corner. If you meant comment moods (an emot on the right superior corner of the comment, you'll find them on the right side of the commenting box...)
I'm not sure if this is clear, let me know if you have any doubts or meant something else...