This is a great way to add a little visibility to your users, it adds an icon next to your file links, showing them visually what it is

I take no credit at all for this, all the credit belongs to http://pooliestudios.com/projects/iconize/ 

This is a great tool - and very simple when you look at it I got rave reviews when I implemented this on our in-house web-based fileshare system at work.  Hopefully it can help you out too!