putting diff. header for diff. categories

I have searched for a long time.
I want to have 2 different header imagses. One will always be there and another one will change based upon what category is being displayed.

basically:
if category 1 is displayed, then show example1.jpg;
if category 2 is displayed, then show example2.jpg

it doesnt need to be automatic. i can point the category to the corrent image i want to show.
i have seen these two:
http://wiki.wordpress.org/?pagename=CategoryImages
http://www.coffee2code.com/archives/2004/06/27/plugin-category-images/
but are different and a bit more complicated than what i need.