Bascially, here is my problem:
I have a background image that is loaded through a wordpress php field in the admin panel, which determines the value of an array in my stylesheet. I want a way to change that background image named "img.bg" in my CSS through a custom field in one of my pages. I basically want that background image to change per page. I understand that I need to modify the value of "img.bg", but the rest is hard for me to grasp due to my limited knowledge of PHP.
Theme used : Big Picture 1.2 by Eugene Okoronkwo
Any help would be appreciated