I have just pulled request the stylesheets (and related image files) I have been developing for a while, now they are at 2.01 version.
If you are not familiarized with them, please, follow this thread for info, screenshots, etc: viewtopic.php?f=9&t=14518
Following a little preview:
As it is the first commit related to stylesheets I have seen it wasn't any folder created to store them so, I think I have correctly placed them into src/Gui/Stylesheets, but if I'm wrong let me know.
I have used spaces into the file names so that when listed into Preferences they look better and be more readable, I have tested them on Ubuntu, Windows and OSX and they work correctly, but, if you want me to rename them let me know.
I have of course, created a pull request at: https://github.com/FreeCAD/FreeCAD/pull/110