Change large image based on option

So, I want the large image on a product page to change automatically when an option is chosen - you'd think this is standard but apparently not.



I have seen this done here:



http://www.thebutter…rfly-decor.html



Any idea how this was achieved?

I found this eventually - for anyone else looking, rebuild the product options and then you will see the image field.



Looks like you can only have one image per option though?