I want to use more then one theme for my site. Visitor can use his favorate theme on site.
So what I need>>> I can add and delete theme from admin.

Second option if there are no script for select theme I can change theme for whol site with a single click from admin Like graphic, font style etc.

Is any one know scripts for this?

I have a skin switch on my site that is simple, but yet works.

http://watchzine.com/forum.php?forum_id=5&topic_id=194&last_post=1076479216

The first post is where I got the main way how it works. You can delete skins, but to make it in an admin section I recommend storing the headers and footers of each theme in a database and they taking it out of the database depeding on what the user has so then you can have easy admin systems to manage this.