Still under intensive polishing, the Firefox 3 themes now have names: Tango, Strata and Firelight, for the Linux, Windows and Mac OS X operating systems, respectively.
Tango, is named directly after the Tango Desktop Project which provides visual guidelines for Gnome and KDE Linux desktop environments. The new theme is in large part an effort of Michael Ventnor.
Strata, is an invention of Mike Beltzner, one of Firefox 3 lead developers. Icons were commissioned to the Iconfactory.
You will see these images in the Themes tab of upcoming first Firefox 3 release candidate.