Presumably your XSLT stylesheet is generating HTML output. You don't want the image in your XSLT stylesheet, you want it in your HTML output. Do you know what HTML you want to generate? If so, generating an <img> element is just the same as generating any other element. If you don't know what HTML output you want your stylesheet to produce, then you're in the wrong place: you want an HTML forum.
Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference