I would really recommend upgrading to the latest version of Geeklog (currently v1.4.1).
That said, you are correct, the above code is not found in style.css for GL v1.4.0sr5-1. You will probably want to look at:
Text Formatted Code
.header-logobg-container-inner {
background:#FFFFFF;
background:url(images/header-bg.png) #1A3955;
border-bottom:1px solid #CCCCCC
and change the header-bg.png image to whatever you want, jpg, gif, etc. and make sure you upload the corresponding file to your layout/professional/images folder.
In v1.4.0sr5-1 header.thtml, you can adjust the height by changing the two height properties from 78 to whatever:
Text Formatted Code
<table width="100%" border="0" cellpadding="0" cellspacing="0" class="header-logobg-container-inner">
<tr>
<td class="header-logobg" width="50%" height="78" align="left" valign="middle"> <a href="{site_url}/"><img src="{site_logo}" width="151" height="56" alt="{site_name}" border="0"></a></td>
<td class="header-logobg" width="50%" height="78" align="right" valign="middle"><span class="site-slogan">{site_slogan}</span> </td>
</tr>
</table>
Again, I would strongly recommend updating to the latest verison of GL. It should be relatively easy from the version you are running.
Hope this helps!
-Eric
Synergy - Stability - Style --- Visit us at glfusion.org