even though there are is a wide selection of themes to choose from, a very few appeal to me. these are the ones I think most people can use for months without getting tired of them.
Note from Mozilla: This add-on has been discontinued. Try Colorlicious instead.
Change Firefox to Any Color and create your own personalized theme.
A combination of the Firefox 1 default theme "Winestripe" and the Firefox 3 default theme "Strata". StrataStripe is basically the Strata theme with Winestripe buttons. Looks much better.
Whitehart delivers simplicity and unobtrusiveness so you can concentrate in the content that is what matters. It provides configuration from an integrated control panel.
Camifox is elegant, crisp, and colorful. It’s a thoughtful and sophisticated reimagination and realization of a better “default”-like theme for Firefox, in living color on all platforms, inspired by the appearance of the excellent Camino browser.
The official Firefox theme of the Elementary Project
Gnome icons integrated into FireFox thanks to The GNOME Project.