I think you didn't understand what I want

I'll try to be understandable (sorry if I'm not) :
I already have several categories and subcategories
- Nintendo (which is empty, contain just 2 subcategories)
--- Gamecube (which contain nintendo's gamecube pictures)
--- Wii (which contain nintendo's wii pictures)
- Sega (which is empty, just 2 subcategories)
--- dreamcast (which contain sega's dreamcast pictures)
--- saturn (which contain sega's saturn pictures)
So 2 categories which contain 2 subcategories each.
I created a third category which I called "member's pictures" (in the admin panel).
Now I would like each user be able to create their "main category" in member's pictures (which is already a main category).
For having this :
- Member pictures (which is empty)
---user1 (which is the "main category" of the user1 created thank to its UCP)
------nintendo pictures of user1 (which is a subcategory created with UCP by user1)
------sega pictures of user1 (...)
---user2 (which is the "main category" of the user1 created thank to its UCP)
------nintendo pictures of user2 (which is a subcategory created with UCP by user2)
------sega pictures of user2 (...)
To sum up, I'd like this :
- Nintendo
--- Gamecube
--- Wii
- Sega
--- dreamcast
--- saturn
- Member pictures
---user1
------nintendo pictures of user1
------sega pictures of user1
---user2
------nintendo pictures of user2
------sega pictures of user2
And not this :
- Nintendo
--- Gamecube
--- Wii
- Sega
--- dreamcast
--- saturn
- Member pictures
- user1
---nintendo pictures of user1
---sega pictures of user1
- user2
---nintendo pictures of user2
---sega pictures of user2
You think it's possible to do such a thing ?
Thanks a lot
