Heh good one! Very good advice!
and please, no more cars
unless that studio is making only racing games. In fact as mentioned, spend some time to find out what that studio you are applying for a job is doing.
Do not show characters when you are applying as environment artist. You won't be hired. Do not apply for environment artist post if you hope you will be switched later on. You may or may not.
Why? because chances are in a while you'll start thinking you are being "underused", become unhappy and grumpy and start looking for another job
Nobody wants others to be unhappy, when someone is hired it is expected that they will stay with a studio for a while. "Jumpers" also are not very welcome.
Imagination and Creativity are the most valuable commodities.
If you show you got it, you will be preferred over artists with similar technical skills!
Show it with your choice of subject, the detail on your textures, the choice of colours.
Personally i see the entire reel 90% of the cases trying to find signs of talent anywhere that could be cultivated. But the first pieces as well as the last make the most effective impression.
Do not put a lot of art. Only your BEST art. I have seen only one image from an artist who sent his work from an email that was bouncing.. never submitted any other contact information or CV. I wanted to hire him. I never found him
I hired the next guy who was as good.
Moral: Put at least your name and a working email on a small corner of your image in a discreet artistic manner if you do not send CV.