XSLT

gistfile1.xml

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet
	version="1.0"
	xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
	xmlns:umb="urn:umbraco.library"
	exclude-result-prefixes="umb"
>

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

	<xsl:variable name="style" select="tbc" />
	<xsl:variable name="patterns" select="umb:GetXmlDocument('/xslt/grid-patterns.xml' , 1)" />
	<xsl:variable name="patternTotal" select="count($patterns/patterns/pattern [@name = $pattern]/* )" />

	<!-- Grid Blocks -->    
	<xsl:template name="news-block" match="publicNewsArticle">

		<xsl:variable name="seqPosition" select="round((position()-1) div $patternTotal)" />
		<xsl:variable name="index" select="(position()-($seqPosition * $patternTotal))" />
		<xsl:variable name="style" select="$patterns/patterns/pattern/style[number($index)]"/>

		<!-- Image Block -->
		<xsl:if test="$style/@preImage !=''">
			<div class="block"><img src="{$style/@preImage}" /></div>  
		</xsl:if>

		<!-- Article Block -->
		<a href="{umb:NiceUrl(@id)}" class="block {$style/@name}">
			<h2>
				<xsl:value-of select="umb:FormatDateTime(contentDate, 'dd MMMM yyyy')"/>
			</h2>
			<xsl:value-of select="contentTeaser" disable-output-escaping="yes"/>
		</a>
	</xsl:template>

</xsl:stylesheet>

<!-- Input XML Document for Reference -->

<!-- Pattern - XML Document for Reference -->
<?xml version="1.0" encoding="utf-8" ?>
<patterns>
  <pattern name="news">
    <style name="dark" />
    <style name="light" />
    <style name="dark" preImage="http://placehold.it/150x150"/>
    <style name="white" />
    <style name="dark" />
    <style name="light" preImage="http://placehold.it/150x150"/>
    <style name="white" />
  </pattern>
</patterns>