Personas are easy-to-use themes that let you personalize the look of your Firefox says the Personas page. In fact, it is a great collection of many nice pictures you can apply in your Firefox with one click.
Olivier had the great idea to reuse them in LibreOffice too. I provided him with few code pointers to implement the feature, but then I decided this is actually so fun project that I wanted to do it myself (sorry, Olivier!) - and started that at the Munich HackFest. Long story short, here is the result:
Unfortunately we cannot choose Personas in LibreOffice with just one click as in Firefox, but it is as easy as it can be - just download LibreOffice 4.0 RC1 (or later) when available, choose Tools -> Options... -> Personalization -> Select Persona, and the rest is trivial, the dialog will lead you through the necessary steps. Enjoy!