From the FAQ:
It is not necessary to delete your account once you feel that you no longer need it. Simply stop using it. Otherwise send us an email and we will remove it.
http://imageshack.us/content.php?page=email&q=customer
URLS:
http://imageshack.us
http://stream.imageshack.us/content.php?page=email&q=customer
Please note that AccountKiller.com is not associated with the business listed on this page. AccountKiller provides easy-to-understand instructions and guides on how to cancel charges and relationships from the list of businesses on our site, we have no affiliation with these businesses.