<xsl:template match="PrintingImages">
<fo:block keep-together.within-page="always">
<fo:table table-layout="fixed" width="100%" border-collapse="separate" border-separation="2pt" column-width="50pt">
<fo:table-body>
<fo:table-row>
<xsl:apply-templates/>
</fo:table-row>
</fo:table-body>
</fo:table>
<xsl:template match='PrintImagesData'>
<fo:table-cell>
<fo:block keep-together.within-page="always" float="left">
<xsl:if test="Title">
<fo:block><xsl:value-of select="Title" /></fo:block>
</xsl:if>
<xsl:if test="DateCreated">
<fo:block><xsl:value-of select="DateCreated" /></fo:block>
</xsl:if>
<fo:block line-stacking-strategy="max-height">
<xsl:element name="fo:external-graphic">
<xsl:attribute name="width"><xsl:value-of select="Width"/></xsl:attribute>
<xsl:attribute name="height"><xsl:value-of select="Height"/></xsl:attribute>
<xsl:attribute name="content-width">scale-down-to-fit</xsl:attribute>
<xsl:attribute name="content-height">scale-down-to-fit</xsl:attribute>
<xsl:attribute name="scaling">uniform</xsl:attribute>
<xsl:attribute name="src">url('<xsl:value-of select="ImgData"/>')</xsl:attribute>
</xsl:element>
</fo:block>
</fo:block>
On the backend I call PrintImagesData 4 times, and within the PDF, it generates four images on the same line. I want two images on each line (e.g. two rows, two columns). How can I do that?
One option is to create a new fo:table-row at every odd positioned PrintImagesData and then create an fo:table-cell for that PrintImagesData and the first following-sibling PrintImagesData.
Here's an example based on the limited amount of info in the original question...
XML Input
<doc>
<PrintingImages>
<PrintImagesData>
<Title>Title 1</Title>
<Width>100px</Width>
<Height>100px</Height>
<ImgData>some/graphic1.png</ImgData>
</PrintImagesData>
<PrintImagesData>
<Title>Title 2</Title>
<Width>100px</Width>
<Height>100px</Height>
<ImgData>some/graphic2.png</ImgData>
</PrintImagesData>
<PrintImagesData>
<Title>Title 3</Title>
<Width>100px</Width>
<Height>100px</Height>
<ImgData>some/graphic3.png</ImgData>
</PrintImagesData>
<PrintImagesData>
<Title>Title 4</Title>
<Width>100px</Width>
<Height>100px</Height>
<ImgData>some/graphic4.png</ImgData>
</PrintImagesData>
</PrintingImages>
</doc>
XSLT 1.0 (Made a couple of changes to your original XSLT; mainly the use of AVT's.)
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:fo="http://www.w3.org/1999/XSL/Format">
<xsl:output indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:template match="/*">
<fo:root xmlns:fo="http://www.w3.org/1999/XSL/Format">
<fo:layout-master-set>
<fo:simple-page-master master-name="my-page" page-width="8.5in" page-height="11in">
<fo:region-body margin="1in" margin-top="1.5in" margin-bottom="1.5in"/>
</fo:simple-page-master>
</fo:layout-master-set>
<fo:page-sequence master-reference="my-page">
<fo:flow flow-name="xsl-region-body">
<xsl:apply-templates/>
</fo:flow>
</fo:page-sequence>
</fo:root>
</xsl:template>
<xsl:template match="PrintingImages">
<fo:block keep-together.within-page="always">
<fo:table table-layout="fixed" width="100%" border-collapse="separate" border-separation="2pt" column-width="50pt">
<fo:table-body>
<xsl:apply-templates select="PrintImagesData[not(position() mod 2 = 0)]" mode="row"/>
</fo:table-body>
</fo:table>
</fo:block>
</xsl:template>
<xsl:template match="PrintImagesData" mode="row">
<xsl:variable name="nbr">
<xsl:number/>
</xsl:variable>
<fo:table-row>
<xsl:apply-templates select="."/>
<xsl:if test="not($nbr mod 2 = 0)">
<xsl:choose>
<xsl:when test="following-sibling::PrintImagesData">
<xsl:apply-templates select="following-sibling::PrintImagesData[1]"/>
</xsl:when>
<xsl:otherwise>
<fo:table-cell>
<fo:block/>
</fo:table-cell>
</xsl:otherwise>
</xsl:choose>
</xsl:if>
</fo:table-row>
</xsl:template>
<xsl:template match="PrintImagesData">
<fo:table-cell>
<fo:block keep-together.within-page="always" float="left">
<xsl:apply-templates select="Title|DateCreated"/>
<fo:block line-stacking-strategy="max-height">
<fo:external-graphic
width="{Width}"
height="{Height}"
content-width="scale-down-to-fit"
content-height="scale-down-to-fit"
scaling="uniform"
src="url('{ImgData}')"/>
</fo:block>
</fo:block>
</fo:table-cell>
</xsl:template>
<xsl:template match="Title|DateCreated">
<fo:block><xsl:value-of select="."/></fo:block>
</xsl:template>
</xsl:stylesheet>
XSL-FO Output
<fo:root xmlns:fo="http://www.w3.org/1999/XSL/Format">
<fo:layout-master-set>
<fo:simple-page-master master-name="my-page" page-width="8.5in" page-height="11in">
<fo:region-body margin="1in" margin-top="1.5in" margin-bottom="1.5in"/>
</fo:simple-page-master>
</fo:layout-master-set>
<fo:page-sequence master-reference="my-page">
<fo:flow flow-name="xsl-region-body">
<fo:block keep-together.within-page="always">
<fo:table table-layout="fixed" width="100%" border-collapse="separate" border-separation="2pt" column-width="50pt">
<fo:table-body>
<fo:table-row>
<fo:table-cell>
<fo:block keep-together.within-page="always" float="left">
<fo:block>Title 1</fo:block>
<fo:block line-stacking-strategy="max-height">
<fo:external-graphic width="100px" height="100px" content-width="scale-down-to-fit" content-height="scale-down-to-fit" scaling="uniform" src="url('some/graphic1.png')"/>
</fo:block>
</fo:block>
</fo:table-cell>
<fo:table-cell>
<fo:block keep-together.within-page="always" float="left">
<fo:block>Title 2</fo:block>
<fo:block line-stacking-strategy="max-height">
<fo:external-graphic width="100px" height="100px" content-width="scale-down-to-fit" content-height="scale-down-to-fit" scaling="uniform" src="url('some/graphic2.png')"/>
</fo:block>
</fo:block>
</fo:table-cell>
</fo:table-row>
<fo:table-row>
<fo:table-cell>
<fo:block keep-together.within-page="always" float="left">
<fo:block>Title 3</fo:block>
<fo:block line-stacking-strategy="max-height">
<fo:external-graphic width="100px" height="100px" content-width="scale-down-to-fit" content-height="scale-down-to-fit" scaling="uniform" src="url('some/graphic3.png')"/>
</fo:block>
</fo:block>
</fo:table-cell>
<fo:table-cell>
<fo:block keep-together.within-page="always" float="left">
<fo:block>Title 4</fo:block>
<fo:block line-stacking-strategy="max-height">
<fo:external-graphic width="100px" height="100px" content-width="scale-down-to-fit" content-height="scale-down-to-fit" scaling="uniform" src="url('some/graphic4.png')"/>
</fo:block>
</fo:block>
</fo:table-cell>
</fo:table-row>
</fo:table-body>
</fo:table>
</fo:block>
</fo:flow>
</fo:page-sequence>
</fo:root>