What we do here - is add those lines I posted into all our stylesheets. They link to the graphics we use up top - the threadsdev logo and the "swoosh". Try changing stylesheets in My Home and you'll see that they change which image they use.
Then - in our header - we code the HTML like this:
<br /><table width="100%" align="center" cellpadding="1" cellspacing="1" class="tablesurround"><br /><tr><br /><td><br /><table cellpadding="0" cellspacing="1" width="100%" class="tableborders"><br /><tr><br /><td align="left" class="darktable"><br /><table cellpadding="0" cellspacing="0" width="100%"><br /><tr><br /><td width="240" nowrap="nowrap"><br />[:"red"]<img src="https://ubbdev.com/forum/images/cssgraphics/defaults/clearlogo.gif" <br />class="devlogo" width="240" height="75" border="0" alt="ThreadsDev.com" /><br />[/]<br /></td><br /><td align="center" valign="middle"><br /><img src="https://ubbdev.com/forum/images/icons/blank.gif" border="0" alt="UBB.Threads Modifications" /><br /></td><br /><td width="200"><br />[:"red"]<img src="https://ubbdev.com/forum/images/cssgraphics/defaults/cleardevswoosh.gif" <br />class="devswoosh" width="200" height="75" align="right" border="0" alt="ThreadsDev.com" />[/]<br /></td><br /></tr><br /></table><br /></td><br /></tr><br /></table><br /></td><br /></tr><br /></table><br /><br />
The "clear logo" are "blank" image files - like a 1x1 blank gif. set to the size we need. Then it gets applied the class from the stylesheet which contains the logo.