You can change the rating associated with your Gravatar image by following these steps:
- Login to your account at Gravatar.com
- Click "My Gravatars" at the top of the screen
- Select the email address associated with the image you'd like to update
- Scroll down to the image you'd like to use and click the rating beneath it
- Select the appropriate rating for your image
- Click the "Set Rating" button to save your changes
Please note, changes may take up to 24 hours to go into effect.