se la tua intenzione è inserire solo 12 immagini rappresentate quattro in orizzontale per tre in verticale basta fare una tabella sola..
<DIV align=center>
<TABLE border=0 cellpadding=5 cellspacing=5>
<TR>
<TD>[img]pic1.jpg[/img]</IMG>
<TD>[img]pic2.jpg[/img]</IMG>
<TD>[img]pic3.jpg[/img]</IMG>
<TD>[img]pic4.jpg[/img]</IMG>
<TR>
<TD>[img]pic5.jpg[/img]</IMG>
<TD>[img]pic6.jpg[/img]</IMG>
<TD>[img]pic7.jpg[/img]</IMG>
<TD>[img]pic8.jpg[/img]</IMG>
<TR>
<TD>[img]pic9.jpg[/img]</IMG>
<TD>[img]pic10.jpg[/img]</IMG>
<TD>[img]pic11.jpg[/img]</IMG>
<TD>[img]pic12.jpg[/img]</IMG>
</TABLE>
</div>