This rather came up by accident. But it might come in handy: using groups for VIP invitations.
Create a group and set all it’s permissions to Group owners and moderators. So the group is invisible to it’s members.
Add members and don’t inform them.
Create a category and set all it’s permissions so that only group members can access it.
Send a message to the group and invite them to your new category.
(I think that’s a glitch in the Discourse ux: the group is invisible to the user on the Groups page, but shows up in the message)
Present whatever you want in your VIP category.
I used a category image here. By default they show up quite big in the Category list view. I adjusted the image’s size with this solution: