The following command imports a picture to the thumbnailphoto attribute in AD. This can be used by Outlook, Lync, SharePoint and other application to display a users picture.
Import-RecipientDataProperty -Identity “mailbox name” -Picture -FileData ([Byte[]]$(Get-Content -Path “D:Picturesbob.jpg” -Encoding Byte -ReadCount 0))
Thumbnail image must be less than 10k.