Thank you, that worked!
Although, I did have to add ‘true’ as a variable of get_next_post for some reason. Like this:
<?php
$get_previous_post = get_next_post(true);
echo get_wp_user_avatar($get_previous_post->post_author, 96);
?>
<?php
$next_post = get_next_post(true);
echo get_wp_user_avatar($next_post->post_author, 96);
?>
Thank you again for the help and thank you for a terrific plugin!