AX 2012 had a wide variety of icons. The ribbon bar is literary littered with them. In the next version there are almost no icons, but you have probably noticed that there are some here and there. It is solved by using a special Dynamics AX Symbol font.
There are clear best practice guidelines on how to use these and I urge you to follow them, and if you’re in to functional and form design you should be aware. There is a document listing all the different icons and give you the guidelines to use them:
You can also contact the Symbols team if you want to add additional icons. Read about it the document.