1. You can turn on automatic smiley character pattern (also kind of markup) recognition by turning on Option/UseSmileys. Syntax: :-) ;-) :-( =>
2. you can use CdmlSymbol to display smileys as examples for a extensible group of symbols that can be supported through a common mechanism. Syntax: [[symbol]:-)] =>
3. Smileys could also be supported by using the InterWeb abbreviation system. Syntax: Symbol:smile =>

Community considerations

Note that smileys add a joyful or playful touch to a wiki system. Depending on your community this may desirable (e. g. in a SchoolWiki) or undesirable (in a honorable academic environment).