The avatars (i.e. little pictures) alongside readers' comment on Gruts are associated with the email address the commenter supplied when they made their comment.
To set up or change your own avatar, create an account at Gravatar.com, upload your preferred image, and associate it with the email address you use to comment on Gruts. It is dead easy! Once you have registered an avatar, it will work on lots of other websites.
Keep them clean, now, boys and girls!