Walnut2, based on icons from art.gnome.org. Includes support for help, inspector, downloadstatusbar, downloadmgr, calendar, quicknote, offline, toolbarext. and many other extensions. Install "About Home Themer" to also theme the about:home page.
This is PP or Pink Paula. The theme changes Firefox user interface with a nice and light pink style. If you want to get more advanced Pink options, try the PPP version which is an extension. Seach for PPP.