Yosembiance is a nice GTK3 theme that specifically designed for Ubuntu Unity. But here I tried to install this Yosembiance GTK3 theme on my Fedora 21 GNOME and it works. But its not as good as in Ubuntu 14.10 off course. Here are some screenshots of my Fedora 21 desktop with Yosembiance GTK3 theme installed.
To install Yosembiance theme on Fedora, simply follow these steps:
A. Download Yosembiance package
Use Terminal to download Yosembiance package
B. Unzip the package
C. Move theme to /usr/share/themes
sudo mv Yosembiance /usr/share/themes
Now open Gnome Tweak Tool and change theme to Yosembiance.