По умолчанию в шаблоне страницы товара имеется такой вот код:
<?if($SMALL_1$)?>
<img alt="" src="$SMALL$" class="gphoto" onclick="var el=getElementById('ipreview'); el.src='$THUMB$'; el.setAttribute('idx',0);">
<img alt="" src="$SMALL_1$" class="gphoto" onclick="var el=getElementById('ipreview'); el.src='$THUMB_1$'; el.setAttribute('idx',1);">
<?endif?>
<?if($SMALL_2$)?><img alt="" src="$SMALL_2$" class="gphoto" onclick="var el=getElementById('ipreview'); el.src='$THUMB_2$'; el.setAttribute('idx',2);"><?endif?>
<?if($SMALL_3$)?><img alt="" src="$SMALL_3$" class="gphoto" onclick="var el=getElementById('ipreview'); el.src='$THUMB_3$'; el.setAttribute('idx',3);"><?endif?>
соответственно выводит лишь 3 фото, чтобы выводил дополнительные 4, дополните условия и замените код выше на:
<?if($SMALL_1$)?>
<img alt="" src="$SMALL$" class="gphoto" onclick="var el=getElementById('ipreview'); el.src='$THUMB$'; el.setAttribute('idx',0);">
<img alt="" src="$SMALL_1$" class="gphoto" onclick="var el=getElementById('ipreview'); el.src='$THUMB_1$'; el.setAttribute('idx',1);">
<?endif?>
<?if($SMALL_2$)?><img alt="" src="$SMALL_2$" class="gphoto" onclick="var el=getElementById('ipreview'); el.src='$THUMB_2$'; el.setAttribute('idx',2);"><?endif?>
<?if($SMALL_3$)?><img alt="" src="$SMALL_3$" class="gphoto" onclick="var el=getElementById('ipreview'); el.src='$THUMB_3$'; el.setAttribute('idx',3);"><?endif?>
<?if($SMALL_4$)?><img alt="" src="$SMALL_4$" class="gphoto" onclick="var el=getElementById('ipreview'); el.src='$THUMB_4$'; el.setAttribute('idx',4);"><?endif?>
<?if($SMALL_5$)?><img alt="" src="$SMALL_5$" class="gphoto" onclick="var el=getElementById('ipreview'); el.src='$THUMB_5$'; el.setAttribute('idx',5);"><?endif?>
<?if($SMALL_6$)?><img alt="" src="$SMALL_6$" class="gphoto" onclick="var el=getElementById('ipreview'); el.src='$THUMB_6$'; el.setAttribute('idx',6);"><?endif?>
<?if($SMALL_7$)?><img alt="" src="$SMALL_7$" class="gphoto" onclick="var el=getElementById('ipreview'); el.src='$THUMB_7$'; el.setAttribute('idx',7);"><?endif?>