Quick theme changing

Marek Jurman told me about this quick way to change themes; In a nautilus location bar (press Ctrl-L to get one), type in "themes:///" (without the quote-signs off course) and press enter. A nautilus window will open (like a folder) with icons (thumbnails) for every theme on your system. Just click one to quickly apply a theme.
When you want to tweak the theme further, you have to open the theme dialog (where you can also change themes) by System > Preferences > Theme. In this window you can change window borders, window element styles and icons separately.

Have fun!