pay pal pro custom forms dead image link

Hi guys,

so if you go to the following link
http://www.rohr-blog.com/sterling-membership/

to the right of the coupon code field you can see an x as our image is not displaying.upon further research it seems the link is referencing an old development company link. where would i go to update the image link so i can have it display correctly

thanks
nick

https://wordpress.org/plugins/s2member/