I changed to graphic in my form but the old graphic still appears when I distribute the link via Facebook.

How can I make sure only the current graphic is associated with my form?

Hello VAAPResident,

If the old image is the one showing on Facebook, it's most likely be due to the sharer cache of facebook which is causing the issue. 

You can check out these pages for more information on how to clear facebook's sharer cache in order for the new image to load when the link gets shared on their platform:

http://www.idiotinside.com/2016/04/14/clear-facebook-sharer-cache-using-facebook-batch-invalidator/ 

https://www.facebook.com/help/community/question/?id=524084047668000 

https://developers.facebook.com/tools/debug/

If you have questions, please let us know.

Thanks.