I'm kinda surprised nobody's made, or attempted to make, a diecast track before -- as in a track that looks like you're a 1/64 diecast driving on a makeshift track, either on a desk or the floor. Zero banking, walls held together with tape, the flagman is a Lego minifig for some reason (and is therefore like twice the height of the actual cars), the "horizon" is just the rest of the room, some random ass book is one of the walls... there's a TV on in the background...
It's definitely something I would have made if I had the sustained interest to do it (I've abandoned like 30 tracks for that reason, and that isn't a joke), I'm just surprised nobody else has done it, or attempted it. I could be wrong on this, but the only things I'm aware of that come close are that one Hot Wheels track... which doesn't really count because I'm talking about a more serious track.
I mentioned this because I used to have a Poser 8 render scene that was like a diecast on my desk scene. Since it's a Poser 8 scene I don't have it anymore and it didn't look that great.
EDIT: Of course, a day after I wrote this, I started thinking of what I would do for a diecast track... and that answer is basically a track on a table or desk near a window (so that maybe you could see outside of it). Either that, or a track on the floor, which, if it's on carpet, might be, interesting to put it mildly, depending on what kind of carpet it is.
I would also have a TV and computer on in the background. When the caution would come out, the image on the TV and computer would change. Maybe even the things playing on the TV/computer would be different depending on the time in the race weekend (or even have them tied to RandomSky, I haven't successfully done that before, would be a good opportunity to try that). If the track is on the floor, then the TV/computer would be a lot harder to see, because NR2003 doesn't really have your gaze going upwards too often. Even on a track like Zanarkand.
Honestly the geometry for this might be really, really simple unless you wanted to have like, cars to be able to get knocked off the table and go onto the floor. Even a lot of the objects in the background could be really simple because they'd be really far away. Some of the object modeling might be tricky but scale might be the only thing you'd really have to watch (because everything would be 64 times its size unless it was like, meant for the track itself).