if you try to edit style.css every bg (window,cat) will be change

and man sorry it was my mistake ;
Check messageindex.template.php ;
if (!$context['no_topic_listing'])
echo '
<td style="padding-top: 2ex;" class="smalltext">', !empty($modSettings['enableParticipation']) ? '
<img src="' . $settings['images_url'] . '/topic/my_normal_post.gif" alt="" align="middle" /> ' . $txt['participation_caption'] . '<br />' : '', '
<img src="' . $settings['images_url'] . '/topic/normal_post.gif" alt="" align="middle" /> ' . $txt[457] . '<br />
<img src="' . $settings['images_url'] . '/topic/hot_post.gif" alt="" align="middle" /> ' . $txt[454] . '<br />
<img src="' . $settings['images_url'] . '/topic/veryhot_post.gif" alt="" align="middle" /> ' . $txt[455] . '
</td>
<td valign="top" style="padding-top: 2ex;" class="smalltext">
<img src="' . $settings['images_url'] . '/icons/quick_lock.gif" alt="" align="middle" /> ' . $txt[456] . '<br />' . ($modSettings['enableStickyTopics'] == '1' ? '
<img src="' . $settings['images_url'] . '/icons/quick_sticky.gif" alt="" align="middle" /> ' . $txt['smf96'] . '<br />' : '') . ($modSettings['pollMode'] == '1' ? '
<img src="' . $settings['images_url'] . '/topic/normal_poll.gif" alt="" align="middle" /> ' . $txt['smf43'] : '') . '
</td>';Here is icons.. check upway to change with transparent..
i think you can add a code for transparent.. and u can change windowbg to transparent like this ;
<td class="transparent" />and you can remove buttons from that file ;
'markread'