A dark, forest theme.
If You like this theme, please try "Dark Night Arcturus X" theme, which is based on "Dark Night Arcturus" theme, but has more elaborate details and is just nicer, becouse I'm going to end the support for "Dark Night Arcturus" in the near future.
This Add-on is a simple theme.
Which is a set header on thunderbird or firfox also.
Header image is based on galaxy image as show on header.