The following link tells you how to change your avatar. This is done by setting up an account with gravatar. Once done, whenever you post a comment to any wordpress type blog, your chosen picture will appear
Note: you will need to be logged into www.wordpress.com and have an account there (free). The following article requires this for its instructions to work. Once you are there in wordpress.com you can create your gravatar image.
Gravatar Instructions. . . Read More. . .