Because getting examples from the documentation to work is a difficult thing for a newbie already, this is not good to make it even harder for them and not provide the working example media files and streams. My suggestion is to upload a file for each example or create a stream somewhere on the internet and make them constantly available as a part of the documentation. Then hard code the names and paths, this could greatly simplify the first steps.

The idea is that not every media file or stream will work with the example, so the learner will struggle and could potentially get lost thinking things like: "is this a bug in the sample code", "did I compile GSTreamer right", "are my media files fit properly this particular example code", "do I make a mistake on the command line".

Providing media that will 100% work with the example code, like test1.ogg, http://media.freedesktop.org/stream1.avi and stuff like that could really help.