Why don't you create some public galleries for anon to see.
And put all your other non-public albums into say a members album, and lock that down to registered users only.
Also in the block editor you could set the random image block to logged in only if you don't want anon to see it.
and don't forget the settings in GL_Gallery2's own config for anon users.
We have a similar system that you speak of at http://dev.neven57.com
Member albums are created on the fly, but they appear in the members album as sub-albums. Members have total control over their own albums. But since they are created under the members parent album, they have the default permissions of the parent album.
Hope this helps
Also, I have the code to generate a link to the current logged in users own gallery.
FlashYourWeb and Your Gallery with the E2 XML Media Player for Gallery2 - http://www.flashyourweb.com