restricting access to media files

Hi,

I want to allow logged in users to add an image to their classified ad.
When I test this the users seems to have access to all of the files in the media library. I definitely do not want this. Is there some way that I can restrict this access to just the images they upload??

Also in the documentation it says:
If you want to click around and see some of the front end UI stuff just check out our CLASSIFIEDS DEMO site.
I can't find the link to the demo site.

Would really appreciate your help with this.
Many thanks.

Jo