I like a track that lets me keep a medium average speed. It'll have some spots that you can hit the throttle hard and some spots where you slow way down but the average speed needs to be around 40% to 50%. I recently tried putting in a set of three burmed 180 degree turns but it was too tight and brought my average down so I scrapped it. Too bad because it was a lot of work.
I like the idea of putting in a background setting. It sure would make things look better. I change my track quite a bit so I'd have to consider that. I thought about putting something like empty vitamin bottles on the inside of a hairpin turn. That way if you come in too close you'll knock the bottles around.