Hmm... I was checking the current source code and I think the easier way to implement KeyStorm's idea would be making the separator as an image and putting it inside a table.
Check this out (I attached the separator image):
code:
<table border="0" width="100%" cellspacing="0" cellpadding="0">
<tr>
<td background="sigseparator.png">
<img src="sigseparator.png"></td>
</tr>
</table>