AD Photo Edit is a great and user friendly software to upload photo into Active Directory. The thumbnailphoto attribute is used to store user photo which can be used for Outlook, Sharepoint and Lync
The software can be downloaded the from this following website http://www.cjwdev.co.uk/Software/ADPhotoEdit/Info.html
After install the software (not necessary install in the AD), click search for user list
Choose the User and click Edit Image
Click Resize to recommended dimensions as the maximum size of photo is 10KB
In Lync Client, make sure Default corporate picture is selected.
After every is done it will take few hours til 24 hours for all pictures to be shown in Lync Client