Take a picture and open it in an appropriate sound tool, or edit the picture file using a text editor to transplant a sound file's header information onto a picture, and you can play a picture. Examples made from the above picture taken Saturday 22 September during SparkCon 2007 at Vintage 21.
Further developments in this area, including a possible tutorial, will follow. Write to discuss.
Update:
Snapshot of desktop in progress:
Interesting article on digitally induced synesthesia