[Updated to add more info on uploading an image]
We have now enabled gravatars for comments. That’s what the little pictures are next to your names.
If you don’t already have a gravatar tied to the email address you use to comment, WordPress will have autogenerated a cute little monster icon and tied it to your email addy. If you want to choose your own gravatar, then please go to gravatar.com and follow the steps to upload the image of your choice to be tied to that email address – then that image will over-ride the autogenerated monster. [ETA: it usually takes only 5 minutes or so for the new image to propagate, but sometimes it's a little bit longer. Just have patience, and if it hasn't happened within 30 minutes go check your gravatar account again and see whether something's playing up.]
Gravatar is fine with registering avatar icons to pseudonymous email addresses – they will just send a confirmation email so that nobody else can register a gravatar to that email address. Obviously, if you use an actual fake email address, then the confirmation email will go nowhere and you won’t be able to do that.
I know that the avatar-space has pushed the comment number to overlap with the name-space, but I’m getting rid of the comment numbers anyway because they don’t mean much with threaded comments changing the numbers as sub-threads grow. If you want to refer to another comment upthread or in another thread, then please use the comment permalink which sits under the commentor name – that link remains constant no matter how comments may subsequently be rearranged.