Here is what I did...
Create a new group called "Photo Admin" and give it no permissions or anything, just an empty group. Then make the users you want a part of that group.
Then open up your gallery/classes/geeklog/User.php file and edit lines 43 and 59 where it has:
$this->isAdmin = SEC_inGroup('Root', '$uid');
to
$this->isAdmin = SEC_inGroup('Photo Admin', '$uid');
That should work for you.