Repeater Gallery with Modal

I have a image gallery with a modal, written with 2 repeaters. It works, but the modal only shows the first image in the gallery. How do I add a unique id to the images?

<div class="imgbox">
   <img src="<%# Eval("GalleryImage") %>" alt="
<%# EvalText("ImageAlt", true) %>" Class="GalleryImage" />
   <div class="text-wrapper"><%# IfEmpty(Eval("Heading"), "", "
<span class='Heading'>" + Eval
<string>("Heading") + "
</span>") %><%# IfEmpty(Eval("GalleryQuote"), "", "
<span class='GalleryQuote'>" + Eval
<string>("GalleryQuote") + "
</span>") %><%# IfEmpty(Eval("Name"), "", "
<span class='Name'>" + Eval
<string>("Name") + "
</span>") %><%# IfEmpty(Eval("Position"), "", "
<span class='Position'>" + Eval
<string>("Position") + "
</span>") %> <span class="ReadMore">
   <a href="#" data-toggle="modal" data-target='#largeModal'>read more</a>
 </span>
   </div>
 </div>

<!-- Modal -->
 <div class="modal fade" id="largeModal" role="dialog" aria-labelledby="basicModal" aria-hidden="true">
   <div class="modal-dialog modal-lg">
 <div class="modal-content">
   <div class="top">
 <img src="<%# Eval("PopupImage") %>" alt="
<%# EvalText("ImageAlt", true) %>" Class="PopupImage" />
 <button type="button" class="close" data-dismiss="modal">X</button>
   </div>
   <div class="OverlayText"><%# IfEmpty(Eval("GalleryQuote"), "", "
<span class='QuoteOverlay'>" + Eval
<string>("GalleryQuote") + "
</span>") %> <br /><%# IfEmpty(Eval("Name"), "", "
<span class='OverlayName'>" + Eval
<string>("Name") + "
</span>") %><%# IfEmpty(Eval("Position"), "", "
<span class='OverlayPosition'>" + Eval
<string>("Position") + "
</span>") %> </div>
   <div class="bottom">
 <div class="textWrapper"><%# IfEmpty(Eval("Heading"), "", "
<span class='PopupHeading'>" + Eval
<string>("Heading") + "
</span>") %><%# IfEmpty(Eval("DetailedText"), "", "
<span class='DetailedText'>" + Eval
<string>("DetailedText") + "
</span>") %> </div>
   </div>
 </div>
   </div>
 </div>
 </div>