> Input XML has: <img src="someSource" alt="someAlt"/>
> Desired output should be exactly the same...

Did you try the following? I don't have Xalan to test with but it works in
XT: 

<xsl:template match="img">
<xsl:copy-of select="."/>
</xsl:template>

Linda van den Brink


 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list