If you want to remove an Image from your site, but think you may want to use it again at a later date, you can "hide" that image. Simply, click on the name of the Image under "Artwork on your Website" and then check the "Hide this Image" box. Click the "Update" button at the bottom of the screen and the image will no longer be visible on your website.

It will still be visible in your Control Panel though, denoted with text marking it as hidden, and can be un-hidden by you at any time.