Original gtk theme is made by i am just us.
theme is tested under unity. metacity theme included works under gnome-flashback too. However i will improve gnome-flashback support soon.
Theme is dark and linux, so you could vote it up. donations for the work of porting gtk2 themes to gtk3.8-10 are welcome.
http://gnome-look.org/content/show.php/BrownOldWest+for+ubuntu+14.04?content=165274