When you create or edit a category for images there is an option to "Allow Users to Create Sub-Categories".
AdminCP => vBGallery => Add / Edit Categories
- Category Options
-- Allow Users to Create Sub-Categories
AdminCP => vBGallery => Usergroup Permissions => [choose a group]
- Can create categories [x] Yes [ ] No
- Maximum number of categories (Set this to 0 for unlimited.)
This will allow members with access to make categories.
Gallery Navbar => My Stuff => Category Admin