The picture (also known as thumbnails) missing or having different paint is because you have different game data (where your thumbnails are stored ). You need to recreate all thumbnails or make do because it is a lenghty process.
mrluckypantsPress triangle when on the car and select create thumbnail. It takes a few seconds per car, but with 500 cars, it can take hours.
Edit: Yikes, found it will take more than 8 hours to do my garage...
Took about 45 minutes to do my garage which is <500 cars
you guys must have a TON of cars..
(theres an option to do all cars at once...)