Version 4.4 of the Author Image plugin has been released. This version adds width and a height options to the Author Image widget so you can override the size of the actual image file.
For those not using the widget and adding the image directly to their WordPress theme template files, a new function call has been added allowing a size to be specified.
<?php the_author_image_size($width, $height, $author_id = null); ?>
Note: The $author_id parameter is optional. If it is not passed in, the code will attempt to get the current author of the page/post.
Thanks to Eric for the inspiration for this enhancement.