Hello! I have created a theme for xfwm by modifying one called greybird-mac, you see, this theme is somewhat outdated and does not combine well with the current Greybird theme and since I could not find another that worked well, I have modified it a bit to fit ...... ta-da!! (~ _ ~ U) (it's not a great story right?)
PD: Excuse the little creative Name "macbird»I have put it like that, because I was sleepy and I couldn't think of any better.
The theme I have used for firefox is called MX3 and it's available here.
You can download the MacBird theme here.