Site Personalization : Font & Background

I have a website with a masterpage and a page called personalize.

I Want to change the background image of my site using a 开发者_如何学编程dropdownlist from that page. My current background and font are defined in my body

Any idea on how to change my background and font?

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Have the Master page define (public?) a variable for the background image, and have it set a "default" value.

Give the Personalize page the dropdownlist, and in the OnChange event for that list, set the background image variable.