I can tell these are some of your first cars, but some of them aren't that bad, especially for your first time, some of these cars are better than the first time I tried to make schemes.
Some problems I see are that quite a few schemes have obvious seams like the hood of the 18, schemes like the 9 would be improved by shrinking the door numbers, and warped logos like the 20. On the 12 I would also say to change the color of the door number to avoid it blending in with the mountains. Also you seemed to forget to flip the number on the left side of the 1 car.
I know from experience that putting your work out for all to see is nerve wracking, but all in all, there are some major issues but these cars are not bad for a novice painter. If you stick around I am eager to see how you improve your work.