If you are looking for Mac OS X icons for Ubuntu Linux, you may want to try this ieOS7 icon theme. ieOS7 is a icon set for Linux which is similar to Mac icons. Now, installing ieOS7 on Ubuntu and derivatives made easier. Thanks to Noobslab which provided the PPA for many beautiful icon theme for Linux.
Here are some ieOS7 screenshots on my Xubuntu 14.04
How to install ieOS7 on Ubuntu, Xubuntu, Linux Mint
sudo add-apt-repository ppa:noobslab/icons
sudo apt-get update
sudo apt-get install ieos7-icons
Then you will need to install Gnome Tweak Tool, Unity Tweak Tool. In Xubuntu 14.04, go to Setting and click Appearance. You can change the system icon from there. Thank you.
Dont forget to check other beautiful icons here.