No sooner had this idea occurred to me than I read your post! I would love to figure out how to do this, along with a million other potential projects.
Could you like, put it back together with the picture inside so it works, and then draw funny faces or whatever over the picture?
i think maybe if you take the original white board and glue it onto the picture, it would work. but you'd have to be careful not to make it took thick or else the "drawings" will not show up.