iWork '09 owners club
How to hide the preinstalled themes in Keynote
- In Applications, right-click on Keynote and choose Show Package Contents.
- Navigate to Contents/Resources.
- Rename the subdirectory Themes to Themes (disabled) and create a new, empty subdirectory called Themes.
- Start Keynote and enjoy the new clutter-free experience.
Presumably, moving some stuff from Themes (disabled) to Themes will restore it to the theme chooser.