I'm not an Outlook user, but I believe that there are multiple ways of integrating photos with it, such as directly in Exchange, in AD, or even from their MS account. With that said, the following link shows different methods of getting pics from sources such as those and may get you down the right path with a bit of tweaking.
At the highest level, "you can't". Tableau Server does not include "photo" as a part of a user's profile. If you mean something else, please explain.
However, when all is said and done, this is really more of an Outlook / Exchange / Exchange 365 question - Tableau is an analytics tool and has no native capability to talk to an email server. At best, you'd need to handle the process of extracting these photos from Outlook / Exchange yourself, drop them into a folder somewhere, and then build a Tableau viz which utilizes them.
With version 10.1 there is now a profile pic option. I cant figure out how to get those to server now. Has anyone had any luck with this?