Re: Automatic member sub categories?
The "User Name Categories" are created on-the-fly, as display only, so they won't show in your Admin control panel. Just create a category, define it as a Members Gallery, and allow users to create sub-categories of that one. When they go to create a sub-category (under the My Stuff menu), they will only be able to create sub-categories under that one, if that's the only one they have permissions to create under.
Users aren't currently able to add a category icon, but I think Brian may be adding that for the next release.