my System library in Interface Builder contains no image or sound resources etc.
I am currently using the iPhone 3.0 SDK. If you have any idea what I can do to get the default media for Interface Builder it would be appreciated.
I am using the Snow Leopard Developer Preview incase this makes a difference.

I do not believe that there are any system media elements exposed through IB on iPhone, only on the desktop Mac OS X. There are obviously several things (like system button images, backward and forward arrows, etc) that would be useful, but only a small number of them are exposed, and where they are exposed they are exposed through constants you pass to particular classes, not as images and sounds you can use directly.
I recommend filing an enhancement request through bugreporter.