Go to Messages, click Manage Images. Click View Contents next to the Image Directory for which you’d like to view the images. The screen will refresh and the images will appear on the lower half of the screen.

Click Delete This Image next to the Image Filename for the image you’d like to delete. A confirmation screen will appear that will let you know whether or not the image is being used in any messages. Confirm deletion by clicking the button Delete the Image.
 
A confirmation message will appear in red that confirms that the message was deleted. To go back to the Manage Images screen, go to Messages and click Manage Images.