How do I display the thumbnail images when using multi-node picker?

Note: the thumbnail is a child node of the of the "selected" multi-picker.

Here is my XSLT:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE xsl:stylesheet [  <!ENTITY nbsp "&#x00A0;">]>
<xsl:stylesheet
  version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:msxml="urn:schemas-microsoft-com:xslt"
  xmlns:umbraco.library="urn:umbraco.library" xmlns:Exslt.ExsltCommon="urn:Exslt.ExsltCommon" xmlns:Exslt.ExsltDatesAndTimes="urn:Exslt.ExsltDatesAndTimes" xmlns:Exslt.ExsltMath="urn:Exslt.ExsltMath" xmlns:Exslt.ExsltRegularExpressions="urn:Exslt.ExsltRegularExpressions" xmlns:Exslt.ExsltStrings="urn:Exslt.ExsltStrings" xmlns:Exslt.ExsltSets="urn:Exslt.ExsltSets"
  exclude-result-prefixes="msxml
 umbraco.library Exslt.ExsltCommon Exslt.ExsltDatesAndTimes 
Exslt.ExsltMath Exslt.ExsltRegularExpressions Exslt.ExsltStrings 
Exslt.ExsltSets ">


  <xsl:output method="xml" omit-xml-declaration="yes" />

  <xsl:param name="currentPage"/>
    
    <xsl:template match="/">

  <!--
    uComponents: Multi-node Tree Picker - An XSLT example
    =====================================
    The Multi-node Tree Picker data-type will provide XML data based on the nodes you have selected.
    In this example, the property alias name for the Multi-node Tree Picker is "treePicker".
  -->

  <!-- First we check that the Multi-node Tree Picker has any nodeId values -->
  <xsl:if test="$currentPage/relatedLinks/MultiNodePicker/nodeId">
    <div id="related_case_study_links">
      <h1>Related Case Studies</h1>
      <ul>
        <!-- Loop through each of the nodeId values -->
        <xsl:for-each select="$currentPage/relatedLinks/MultiNodePicker/nodeId">
          <!--
 Since we only have the nodeId value, we need to get the actual content 
node using umbraco.library's GetXmlNodeById method -->
          <!--
 If you prefer to use pure XPath, then used this: 
"$currentPage/ancestor-or-self::*[@isDoc and @level = 
1]/descendant-or-self::*[@isDoc and @id = current()]" -->
          <xsl:variable name="node" select="umbraco.library:GetXmlNodeById(.)" />
          <li>
            <!-- Output the URL using umbraco.library's NiceUrl method -->
            <a href="{umbraco.library:NiceUrl(.)}">
              <xsl:value-of select="$node/@nodeName" />
                        
              <img src="{concat(substring-before(projectImage,'.'), '_thumb_180.jpg')}"/>
              
            </a>
          </li>
        </xsl:for-each>
      </ul>
    </div>
  </xsl:if>

</xsl:template>

</xsl:stylesheet>