At least 1024x768. Real or real-ish (tried to find a screenshot from the new Forza, but they all had GUI overlay). Preferably with the dashboard. I was trying to find an image as close to what a person sees when they are driving. I know someone with a GoPro, might have to borrow that...
There might be something here: http://www.reddit.com/r/dashcam just don't burn too much time there. Reddit is a god awful time sink and you WILL hate yourself for it.
I had thought about just taking a picture while I drive, but I figured that might a challenge. Might just find a non-busy road and stop and take a picture in the middle of the road.