I've released a persona for Firefox :) All you need to do is download the two files below and follow this instructions.
Simply click on the files and right-click>Save Image
Click on the Fox Face in the bottom left hand corner of the browser, and click on Custom Persona. Put '22520-orig.jpg' (The first image) as the header and '1437987_orig.jpg' (the second image) as the footer or bottom image. Save it and Apply the persona.
Uninstall Personas Plus. Restart.
Enjoy your new look browser!