You can access any Mac icon on your system by opening the Get Info pane, selecting the icon and copying it to your clipboard. If you want to access the system icons, such as the laptop symbols, the warning triangle, folder designs, the generic icons such as disks, the ‘everyone’ icon used in Get Info, plus many others you can. It is very simple as every icon is stored in one folder.
Find System Icons
To find system icons open Finder, select Go from the menu bar, and open Go To Folder. Enter the following address, copy and paste it into the box.
When you hit enter a folder will appear with every icon you want.
To save out the icon you want, double click it to open it within Finder. Then select File > Save As (hold down alt key) and save the icon as a png in your user folders. You now have access to many default icons used through out your system.
I assume that if you change an icon in this folder, it will be changed on your system. I have not tried it, however I wouldn’t recommend it.