I downloaded \"Office 2010 Add-In: Icons Gallery\" that is docx file with two backstage tabs that hold icons.
How can I extract the icons or use them in my application?<
This article contains code that worked for me. They even linked the outputted icon sets in transparent PNGs in the article too, so that you don't need to run the code. I've copied the transparent PNG's links from the article below.
Images 1
Images 2
Note:
Although the icons had a transparent background only the image within the icon was transparent, I had to go into Photoshop and remove the white background manually at the top and bottom. Here's an example: