The profile picture for your account is typically chosen from a set of default icons when you first setup your Mac. This picture is displayed during login and also for your contact in apps such as Mail, Messages and Contacts.
You can change the picture using a picture file on your Mac or take a picture with the built-in camera. OS X Mavericks comes with the options to select photo from your iCloud Photo Stream and also from iPhoto/Aperture libraries.
Go to System Preferences > Users & Groups, select your account on the left and click on your account picture. On the drop-down window, select the “iCloud” tab to select from photos in your Photo Stream. If you’ve setup iCloud and Photo Stream on your Mac, the pictures you took on your iPhone will appear for your selection.
The “Faces” tab on the drop-down window allows you to select tagged Faces photos in your iPhoto or Aperture libraries.