[Spank]

Ok this looks like it does what you're asking:

In template navbar find:

<!-- / breadcrumb, login, pm info -->

Above, add:

<table>
<tr>
     <td> <img src="http://www.YOUR-IMAGE/LOCATION.GIF"></td>
</tr>
<tr>
     <td> <center> Insert Advertisement info here</cewnter></td>
<tr>
     <td> <img src="http://www.YOUR-IMAGE/LOCATION.GIF"></td>
</tr>
</table>

See attachment of how it looked on my board. Hope this helps.