I am considering a smiley update for the next redesign of the site; we need higher resolutions for today's high-pixel-density displays and smartphones. However, I probably won't increase the selection of smilies by much, if at all. We used to have hundreds, but too many built-in smilies makes it difficult to find the one you actually need (this is an issue I have with the emoji selection in smartphone keyboards). I narrowed down the list to faces that actually display common emotions so people can make their text more expressive, and it's worked out quite well over the years, I think.
You can still embed smilies from other sites, and I think they offer a much better home for the little guys, if there's a specific image or obscure emotion that you want to share.