I vote to change them: the current ones are too big and too ambiguous.
As to what style to use instead, I'd go for the standard small smileys seen on What If Modellers and most other web forums.
Regarding the selection of smileys, while it's fine to include quirky, amusing or even custom ones, it's VERY IMPORTANT to have a full suite of the basics, i.e. smile, laugh, frown, angry, rolleyes, wink, thumbs up, thumbs down, confused, shocked (i.e. popping eyes), blush etc.. These are the ones that you actually use most often and in the way there were intended: to convey emotion.