List<Image> images = ......getImages();

for(int i = 0; i < images.size(); i ++)　{
　　　if(i % 3 == 0){
         换行
     } else {
         Image image = images.get(i);
         放置图片和说明
     }
}

------解决方案--------------------
Java code

<tag:forEach var="currentImage" items="${sessionScope|requestScopt.Image}" varState="status">
<tag:if test="${status.index%3==0}"
<tr>
</tag:if>
<td><img ....scr="${currentImage.ImageShow}"/></td>
</tag:forEach