Gravatar is a service for providing globally unique avatars which was created by Tom Preston-Werner and is currently owned by Automattic. Gravatar is widely used by various websites and blogs in order to provide profile pictures to their users directly from their Gravatar accounts. Srinivas Tamada from 9Lessons has a very useful conecpt of using Gravatar pictures along with a login box.
He has designed a simple interesting login box with contains Gravatar image, just importing user avatar from Gravatar.com based on email ID. This concept uses very basic level CSS implementation and few lines of Jquery and PHP code.