Mi iconera social en un blog tengo puesto esto en single.php justo debajo del argumento the_content:
Insertar CODE, HTML o PHP:
<ul>
<li><a rel="nofollow" title="RSS" href="<?php bloginfo('rss2_url'); ?>" rel="nofollow">
<img alt="RSS" title="RSS" src="<?php bloginfo('template_url'); ?>/images/rss_32.png" /></a>
</li>
<li><a rel="nofollow" title="del.icio.us" href="http://delicious.com/post?url=<?php the_permalink(); ?>&title=<?php echo urlencode(get_the_title($id)); ?>" rel="nofollow">
<img alt="del.icio.us" title="del.icio.us" src="<?php bloginfo('template_url'); ?>/images/delicious_32.png" /></a>
</li>
<li><a rel="nofollow" title="StumbleUpon" href="http://www.stumbleupon.com/submit?url=<?php the_permalink(); ?>&title=<?php echo urlencode(get_the_title($id)); ?>" rel="nofollow">
<img alt="StumbleUpon" title="StumbleUpon" src="<?php bloginfo('template_url'); ?>/images/stumbleupon_32.png" /></a>
</li>
<li><a rel="nofollow" title="Digg" href="http://digg.com/submit?phase=2&url=<?php the_permalink(); ?>" rel="nofollow">
<img alt="Digg" title="Digg" src="<?php bloginfo('template_url'); ?>/images/digg_32.png" /></a>
</li>
<li><a rel="nofollow" title="Facebook" href="http://www.facebook.com/sharer.php?u=<?php the_permalink();?>&t=<?php echo urlencode(get_the_title($id)); ?>" rel="nofollow">
<img alt="Facebook" title="Facebook" src="<?php bloginfo('template_url'); ?>/images/facebook_32.png" /></a>
</li>
<li><a rel="nofollow" title="Twitter" href="http://twitter.com/home?status=<?php echo urlencode("Estoy leyendo: "); ?><?php the_permalink(); ?>" rel="nofollow">
<img alt="Twitter" title="Twitter" src="<?php bloginfo('template_url'); ?>/images/twitter_32.png" /></a>
</li>
<li><a rel="nofollow" title="Technorati" href="http://technorati.com/faves?add=<?php bloginfo('url'); ?>" rel="nofollow">
<img alt="Technorati" title="Technorati" src="<?php bloginfo('template_url'); ?>/images/technorati_32.png" /></a>
</li>
<li><a rel="nofollow" title="NewsVine" href="http://www.newsvine.com/_tools/seed&save?u=<?php the_permalink(); ?>&h=<?php echo urlencode(get_the_title($id)); ?>" rel="nofollow">
<img alt="NewsVine" title="NewsVine" src="<?php bloginfo('template_url'); ?>/images/newsvine_32.png" /></a>
</li>
<li><a rel="nofollow" title="LinkedIn" href="http://www.linkedin.com/shareArticle?mini=true&url=<?php the_permalink(); ?>&title=<?php echo urlencode(get_the_title($id)); ?>&source=<?php bloginfo('name'); ?>&summary=<?php the_excerpt_rss(); ?>" rel="nofollow">
<img alt="LinkedIn" title="LinkedIn" src="<?php bloginfo('template_url'); ?>/images/linkedin_32.png" /></a>
</li>
<?php if(function_exists('wp_email')) { ?><li><a rel="nofollow" title="Enviar por correo" href="<?php the_permalink(); ?>&email=1" rel="nofollow">
<img alt="Envia este articulo por correo" title="Enviar por email" src="<?php bloginfo('template_url'); ?>/images/email_32.png" /></a>
</li><?php } ?>
</ul>
Tal vez algun codigo te fallo, o la URL de la imagen no es correcta.