Re: Members on gallery
1). Yes. If you go to the 'Category Admin' link under 'My Stuff' in the gallery navbar then you will see the options for this.
2). As mentioned above, the subscriptions is just an email subscription. However, you can set which usergroups are allowed to add categories, so it shouldn't be a problem to set up a paid subscription with vBulletin and let that update the user's usergroup.