master.xml

<data>
	<entry id="1">
		<title>Title 1</title>
		<gallery>
			<item>
				<image>Image 1</image>
			</item>
		</gallery>
	</entry>
	<entry id="2">
		<title>Title 2</title>
		<gallery>
			<item>
				<image>Image 2a</image>
			</item>
			<item>
				<image>Image 2b</image>
			</item>
		</gallery>
	</entry>
</data>

master.xsl

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">

  <xsl:output method="xml" indent="yes" />

  <xsl:template match="/data">
    <xsl:apply-templates select="entry" />
  </xsl:template>
  
  <xsl:template match="entry">
    
    <!-- Get title -->
    <xsl:value-of select="title" />
    
    <!-- Get images -->
    <xsl:apply-templates select="gallery/item/image" />
  </xsl:template>
  
  <xsl:template match="item/image">
    <xsl:value-of select="." />
  </xsl:template>

</xsl:stylesheet>