This post is about transforming Elementary OS Freya into OS X Yosemite (only the appearance ;-) ). If you’re on eOS Freya, type the below command into the terminal

sudo add-apt-repository ppa:gnome3-team/gnome3 && sudo add-apt-repository ppa:gnome3-team/gnome3-staging && sudo add-apt-repository ppa:ricotz/testing && sudo add-apt-repository ppa:elementary-os/daily && sudo apt-get update && sudo apt-get dist-upgrade -y

Above command will add the latest gnome and elmentary daily PPAs to your system and perform a distribution upgrade. After that type below command in-order to install nautilus and epiphany.

sudo apt-get install epiphany-browser nautilus

Now you can download the XGtk theme from this link and place the theme folder within /usr/share/theme and apply xGtk using elementary-tweak. Now reboot your pc and if everything goes well, your desktop will look as below.

A huge thank goes to Camilo Higuita for creating this wonderful theme and for providing the instructions.