Add Post Image Attribution

On the Edit post panel, at the bottom of the Custom Fields section, click “Enter new”.

In the “Name” field, type image_source, and in the “Value” field, paste the URL you wish to use to link to as the attribution/source.

Click the “Add Custom Field” button; and then the “Publish/Update Post” button.

Then, place this code in custom_functions.php:

function image_source() {
global $post;
$source = get_post_meta($post->ID, 'image_source', true);
  if ($source)
    echo '<p><a href="' . $source . '" rel="nofollow" target="_blank">Image Source</a></p>';
}

add_action('thesis_hook_after_post','image_source');

Note: After the first time you add the image_source custom field to a post, you’ll then be able to simply choose it from the drop down selector under “Add new custom field”, rather than having to choose “Enter new” again.

Based on code from Kristarella (@kristarella).