wpmu-ization of the amazing grace theme

anyone interested in helping or taking upon him/her -self the task to modify the amazing grace theme so that users can customize the random pictures that are used in the header of the theme?

here is another similar thread I started over on the regular forums: http://mu.wordpress.org/forums/topic/12163?replies=6

can it be easily done? what approach would you go in terms of the folder where the images come from?