Hi,
I think that
Web Parts documentation could be helpful for you in many more cases.
Simply find the Web Part you want to use, e.g.
CommentView properties. Where you will find the description:
Enable user pictures: Indicates if user picture ("avatar") should be displayed if it's specified for the comment author.
So user must have
Avatar selected in his profile.
You can see the Avatar picture also in
example blog of Corporate site under
Community/Blogs/Andrew-Jones-Blog/March-2011/Expanding-to-Europe.aspx ... avatar is shown for user Andrew Jones who has already avatar associated with his profile.
Best Regards,
Martin Danko