What is the best method to customize the display of author information on a node of a certain type?
In your code at

 $node-&gt;field_blog_image['und'][0]


this is still an array so you need to access the value of the field one more level deep in to that array you can access it as follows.

$node-&gt;field_blog_image['und'][0]['safe_value']


Rest of code looks good to me.