I just did this in postbit legacy:
Code:
<!-- sig -->
<div></br></br></br></br></br></br>
<center><img src="http://www.yoursite.com/forums/images/misc/line2.gif"/></center><br/><br/><br />
$post[signature]
</div>
<!-- / sig -->
just add your own line gif, such as:
then add as many </br>'s as it takes above or below this code to get the look you want
http://img.photobucket.com/albums/v451/jecdev/sig.jpg