You can delete your account & remove your images and personal data by doing the following:
Click on the Playground logo on the top left of your screen and then select Settings
Click Delete Account in the Account panel
You'll be prompted to confirm your deletion request by typing in your account name and then clicking Delete Account.
NOTE: if you have an active paid subscription, you will need to first cancel that subscription before you can delete your account. Instructions for cancelling your paid subscription are here.