Use the link to delete your account (or deactivate it, if you’re not certain yet).
About data retention, a message from an anonymous visitor of our site may tell something more: I believe they keep the pictures on purpose, since – they keep your password (if you try to log in to a deleted account, the error message will be different if you indicate the proper password or if you indicate an erroneous one). Most likely, they just keep all account info somewhere to perform some (..) datamining on it… It’s no wonder they call themselves “the Google of online dating”.
By the way, it’s AK’s opinion that this is not really exceptional. Most (big, serious, commercial) sites will keep records, if only because they need to legally – for some time.