You can now make Ubuntu or Linux Mint looks like Windows 8 easily, just follow these simple steps.
Run these commands, one by one :
sudo add-apt-repository ppa:noobslab/themes
sudo add-apt-repository ppa:noobslab/icons
sudo apt-get update
sudo apt-get install win-themes
sudo apt-get install win-icons
We can now change theme to win-theme and icons to win-icons using one of these tools : Ubuntu Tweak, gnome-tweak-tool, Unity Tweak Tool ...
Enjoy !