Add gravatar to author list

Question

I am using this code for listing out all authors on the site in my sidebar. It works, except I also need to pull in their Gravatar image. It's working in a loop on the homepage with this

<?php echo get_avatar( get_the_author_email(), '80' ); ?>

but is there a way I can add it to this list as well? Also.. I can't figure out a way to exclude the "Admin" account using this code, is that possible?

Thank you!

<?php
$order = 'user_nicename';
$user_ids = $wpdb->get_col("SELECT ID FROM $wpdb->users ORDER BY $order"); // query users
foreach($user_ids as $user_id) : 
$user = get_userdata($user_id);
?>
<li><?php echo '<a href="' . $user->user_url . '">' . $user->display_name . '</a>'; ?><br /></li>
<?php
endforeach; 
?>

Answer 1

Basic setup

<?php

    $args = array( 'orderby' => 'nicename' );
    $users = get_users( $args ); 

    foreach ( $users as $user ) {
        $avatar = get_avatar( $user->ID, '80' );
        echo '<li><a href="' .
                $user->user_url .
            '">' .
                $avatar . '<br />' .
                $user->display_name .
            '</a></li>';
    }

 ?>

Excluding the Admin User

Either check in the foreach:

foreach ( $users as $user ) {
    if( ! in_array( 'administrator', $user->roles ) ) {
        // echo user list
    }
}

or if all other users are subscribers, include the role parameter as an argument for the user query:

$args = array(
    'orderby' => 'nicename',
    'role' => 'subscriber'
);

or, if you have but one (or few static) admin user, exclude him/her from the query by id:

$args = array(
    'orderby' => 'nicename',
    'exclude' => array( 1, 23 ) //adjust
);

Answer 2

Here's a simple example showing default avatars and lists all users with the role of author.

foreach ( get_users( array( 'role' => 'author'  ) ) as $user )
{
    echo get_avatar(
        $user->ID,
        '96',
        get_stylesheet_directory_uri().'/default-avatar.png',
        $user->nice_name
    );
}

Answer 3

use <?php echo get_avatar( $user->ID, '80' ); ?>, somewhere inside the foreach loop

If you're looking to exclude a particular user, you can use it's id($user->ID) or username($user->user_login) or if you want to exclude all the administrators, you can use if(current_user_can('promote_users')) continue; as the first line of foreach. Check out the reference for more info

http://codex.wordpress.org/Function_Reference/current_user_can