OK - don't mean to dishearten you or anything - but that's not really 'showing
your work' is it?
But we can fix that.
There are some really great tutorials out there for making your own racetrack/road/city in sketchup. It is the easiest 3d modeller available and with a little patience you can be making you own basic game models within 30 minutes.
Think of what you would like to make, search around these forums and google, and then make it. I promise you - you can do it.