Ah, OK, I found the problem and fixed the issue with single entries and the screwed up header. I had messed up something in my functions. Just for your patience, good readers, here is my code for the title that includes an author gravatar:
// Let's put our author gravatar in the post header.
function childtheme_override_postheader_posttitle() {
global $authordata;
if (is_single() || is_page()) {
$posttitle = '<h1 class="entry-title"><span class="title-author-gravatar"><a href="';
$posttitle .= get_author_posts_url($authordata->ID, $authordata->user_nicename);
$posttitle .= '" title="' . __('View all posts by ', 'thematic') . get_the_author_meta( 'display_name' ) . '">';
$posttitle .= get_avatar( get_the_author_email(), '40' );
$posttitle .= '</a></span><a href="';
$posttitle .= apply_filters('the_permalink', get_permalink());
$posttitle .= '" title="';
$posttitle .= __('Permalink to ', 'thematic') . the_title_attribute('echo=0');
$posttitle .= '" rel="bookmark">';
$posttitle .= get_the_title();
$posttitle .= "</a></h1>\n";
} elseif (is_404()) {
$posttitle = '<h1 class="entry-title">' . __('Not Found', 'thematic') . "</h1>\n";
} else {
$posttitle = '<h2 class="entry-title"><span class="title-author-gravatar"><a href="';
$posttitle .= get_author_posts_url($authordata->ID, $authordata->user_nicename);
$posttitle .= '" title="' . __('View all posts by ', 'thematic') . get_the_author_meta( 'display_name' ) . '">';
$posttitle .= get_avatar( get_the_author_email(), '40' );
$posttitle .= '</a></span><a href="';
$posttitle .= apply_filters('the_permalink', get_permalink());
$posttitle .= '" title="';
$posttitle .= __('Permalink to ', 'thematic') . the_title_attribute('echo=0');
$posttitle .= '" rel="bookmark">';
$posttitle .= get_the_title();
$posttitle .= "</a></h2>\n";
}
return apply_filters('thematic_postheader_posttitle',$posttitle);
}
However, the background image still isn't showing.