Open the dialog "Customize the Quick Access Toolbar".
In the dialog box select a section in "Choose commands from:" and go with the mouse over the required command. The tooltip will show the underlying command and in parentheses the appropriate idMSO for the command and the assigned icon.
In Sample DB 3 you can find all possible "Icons" on tab "IconGallerie" in the group "Office Icons". By click on the desired icon a form will open and you can copy "imageMso".
In the link list you will also find a link to the ControlID list. In there you will find all idMso of Office 2007.