On photographers website, the client can login and few his/her pictures - on a guitarbuilders website, the client can login and see updates on the work on their custom guitar - on a skydivers website, the client can login and see the video of their skydive.

create a private page per user
only the user can see the page
use any plugin codes in the content to add video, image, module etc.
link to the page with 1 menu-item for all users
tags like

{username}

scripts which you can call with tags like

{script 2}

for dynamic content from PHP
If you need to display user specific private content. When no private content is set for that user, a default custom message is displayed. When there is content set for that user, the user will need to login to view the user private content. The private content is rendered via the content plugins, so you can use any plugin codes in the user specific content. So you can add video, images, modules and all the goodness of Joomla extensions