A theme provides a style.css file, and any associated images to give ikiwiki a nice look and feel. The local.css CSS file is left free for you to further customize.
Ikiwiki now comes with several themes contributed by users. You can enable the theme plugin to use any of these:
The actiontabs theme, contributed by svend. This style sheet displays the action list (Edit, RecentChanges, etc.) as tabs.
The blueview theme, contributed by BerndZeimetz, featuring a tiling panoramic photo he took.
The monochrome theme, based on Jon's homepage design.