There are so many scripts that will do this for you and as good as it is to be knee deep in Power Shell, sometimes it’s handy to have a decent GUI tool knocking about. My favorite (and one of the only ones that I have seen that does what it says on the tin) is Bulk AD Users by WiseSoft It’s as simple as a connecting to your AD DS instance and updating the attribute that you want to change. In this case, unless there are other requirements, I recommend using the thumbnailPhoto attribute as it interfaces nicely with Exchange and SharePoint 2010.