How to remove your Dreamstime account
According to their FAQ:
Accounts can be removed only if you have no activity registered (uploads, downloads, comments,blogs etc). To delete your account, please go to your Management Area / Edit profile and scroll down for the Delete account button.
Helpful Trick: Removing online data
Helpful Trick: Remove third-party logins
If you signed up for Dreamstime using a third-party login such as Facebook or Twitter, you probably want to revoke all access from Dreamstime. Click here to find out how.