When working with the Content Query Web Part.
Export then editing the Web part to use custom fields
<property name="CommonViewFields" type="string">CustomField1, Text;CustomField2, Number;</property>
Output all available parameters in the ItemStyle.csl
<ul> <li>Specific Variable: <xsl:value-of select="$SafeImageUrl"></xsl:value-of></li> <li>Specific Parameter: <xsl:value-of select="@SafeImageUrl"></xsl:value-of></li> <xsl:for-each select="@*"> <li>P:<xsl:value-of select="name()" /></li> </xsl:for-each> </ul>