Powerpoint always inserts a Loudspeaker icon to represent sounds (e.g. mp3)
on a slide.
How do you change this icon to a picture of your own choosing?
Tagging onto Lucy's answer:
You can also add a Play Sound action to any shape you like, including pictures.
Rightclick the shape, choose Action Settings.
In the Action Settings dialog box, put a check next to Play Sound then choose
one of the existing sounds or scroll down to Other Sound and browse to the
sound you want to insert.
Note: This only accepts WAV sounds (though CDEX might be able to fool PPT into
accepting an MPG as a WAV), and any sounds added this way are *always*
embedded. That's often just what you'd want to happen, of course.