Once you have installed Service Pack 1 for Server 2008 R2 or Windows 7, you can remove the installation files if you won't be uninstalling the service pack.
Online image: DISM /online /cleanup-Image /SPSuperseded
Offline image: DISM /image:<Root Path of Offline Image> /cleanup-Image /SPSuperseded
This is handy to do post-Sysprep and pre-ImageX.