Dark Sublime is a SIMBL extension for OS X that darkens Sublime Text 3's window title bar.
Dark Sublime uses Theos by DHowett. Just make package install to install the package. Installing the .deb will fail as it requires superuser permission, but the package will be manually installed to the right directory. After installing, open EasySIMBL and enable the Plugin. Restart Sublime Text and have fun.
Hovering over the window buttons (close, minimize, maximize) adds a bad-looking white line above those buttons. This is being looked into, pull requests are welcome.
Dark Sublime uses SIMBL and requires EasySIMBL.
The titlebar image is taken from SL3's Soda Theme I also recommend using soda in combination with this plugin.
Thanks to kirb for helping me getting started with SIMBL plugins.