XSL - Extracting a list of images

Hi all

This might sound a dumb question, perhaps my brain isn't what it should be today, I guess it's also just an XSLT question too...

Given a "normal", average-sized docbook document, what XSLT do I need to get myself a list of all the images included in the document.

ie. I have a number of ...<imagedata fileref="myfile1.png"/>... type elements spread liberally through my docbook XML and I want to produce a list that's like:

myfile1.png
myfile2.png
myfile3.png
etc.

TIA.

P.