Hi Nick
If you mean the landing page, then yes you can change the Icons. The landing page is made up of buttons and the button text is an HTML text. Remember that customizing out of the box content will mean you will need to do some work if you upgrade components as a component upgrade will involve reverting to the Out of the Box configuration.
Chris Davidson's Article Apptio report icon library.pdf Shows the Icons that are already available to you in Apptio.
Gregory Nutt's article is a great walk through on how to do this within an HTML box. Remember that the Button Text is HTML so you can apply the information from these articles.
I would practice in a test report before you change the landing page as it will affect everyone in your company that uses Apptio.
David Eyres
Premier Customer Success Manager