Can't you just turn the smileys into .pngs and the white stuff will be invisible? The detective one, and the sweat drip both seem to be like this already, but I think they're .gifs. I know .pngs are a bit bigger, but I don't think the increased size should be too much trouble. Then again, the increased size might shoot bandwith for the server up a bit, even if it is 5kb at a time.
You don't need to make the white stuff invisible, just need to make it dark instead of light. In such a case PNG would compress smaller than GIF, but even if you did go the invisible route with alpha transparency, the size would still be trivial. Animated PNG support is almost nonexistent, though, so the couple animated ones would basically still need to be GIF.
Either way, the issue is doing the work, which would be rather boring. :p I started on it, but I figured it'd be more worth my time to work on PS-themed ones (not that I started on that, either - yay lazyness :p).
About two hours later...Little sloppy, but they should suffice.
http://reisio.com/karyuu-smilies.tar
