Change admin avatar only (without Gravatar or plugin)?

I might have found a solution. It seems to work, but maybe I am missing something?

function custom_user_avatar( $avatar, $id_or_email, $size, $default, $alt ) {
    $user = false;
    if ( is_numeric( $id_or_email ) ) {
        $id = (int) $id_or_email;
        $user = get_user_by( 'id' , $id );
    } else if ( is_object( $id_or_email ) ) {
        if ( ! empty( $id_or_email->user_id ) ) {
            $id = (int) $id_or_email->user_id;
            $user = get_user_by( 'id' , $id );
        }
    } else {
        $user = get_user_by( 'email', $id_or_email );
    }
    if ( $user && is_object( $user ) ) {

        if ( $user->data->ID == '1' ) {
            $avatar = sprintf( '%s/images/avatar/support-male.png', get_stylesheet_directory_uri() );
            $avatar = "<img alt="{$alt}" src="https://wordpress.stackexchange.com/questions/353041/{$avatar}" class="avatar avatar-{$size} photo" height="{$size}" width="{$size}" />";
        }
        else if ( $user->data->ID == '200' ) {
            $avatar = sprintf( '%s/images/avatar/support-female.png', get_stylesheet_directory_uri() );
            $avatar = "<img alt="{$alt}" src="https://wordpress.stackexchange.com/questions/353041/{$avatar}" class="avatar avatar-{$size} photo" height="{$size}" width="{$size}" />";
        }
        else {
            $avatar = sprintf( '%s/images/avatar/default.png', get_stylesheet_directory_uri() );
            $avatar = "<img alt="{$alt}" src="https://wordpress.stackexchange.com/questions/353041/{$avatar}" class="avatar avatar-{$size} photo" height="{$size}" width="{$size}" />";
        }
    }
    return $avatar;
}
add_filter( 'get_avatar' , 'custom_user_avatar' , 1 , 5 );