Changing your profile picture is no longer part of editing your profile, as it was before. In order to choose a new profile picture, simple go to your profile and mouse over your picture. In the top left corner it will say "change" and when you click that, a pop-up will appear in which you can change your profile picture.
The option to use your Gravatar account as a profile picture has also been added! A Gravatar is a Globally Recognized Avatar. You upload it and create your profile just once, and then when you participate in any Gravatar-enabled site, your Gravatar image will automatically follow you there.