xinu is too busy working in production environments, I spent about 15 minutes reading through different articles Google found on the subject. Here's a brief result:extremeexperts article summary: if the images are small and need security, use a DB. If the images are big or requested frequently, use the filesystem. The article also has a link regarding the TerraServer, which stores all its images (8 terabytes) in a database.
Here are some fetch statistics, too.
Community memories would come in handy, if the admin ever felt so inclined. *hinthint*
