Change Author image for featured image

Hello Tim and everyone,

I would like to know how to change the author image for the featured image that is set on the post. So instead of showing the %post_author_avatar% I would like to show %post_thumbnail% or something like that. I have already change in options.php those parameters but didn’t work. I’m in WP version 3.2.1 and BIB version 1.0.7

Thank you very much in advance.

Raul