Eric,
I think I have found how to make pictures, music and videos to appear:
1. Place music in "My Music", pictures in "My Pictures" and videos in "My Videos" (it appears to be case sensitive)
2. Access the MSS Shared Folder Management and click "Manage Digital Photos, Music, Video"
Assuming you already have shared the folder containing your media:
3. Click "Refresh" and the content in your folders should appear on your PS3.
Note from the help file:
"By default the Media Server automatically searches for new media files every two (2) hours. To perform an immediate update to the Media Server database, you must refresh it." - meaning if you add new content it might not appear in another two hours. No wonder I had problems finding media when I tried moving it along all the time

Regards,
Sjur