They are pretty good. I like 7th Golf pic. As a start, you should increase brightness on your pictures, this can be done with either photoshop or Gran turismo 4. Also, when uploading images to imageshack, tick the box with "Remove bar from thumbnail" wich makes your thumbnails look better. Also, if you make a load of shots as you do, only pick a few. At most 3 per car, else people won't be looking, and i don't think you want that do you?
Anyways, you're doing fine and of course, when you're new you want your pictures centered on the car, i used to do that too but if you pay good attention to feedback people give you, and maybe you find useful tips to use, and you'll get better and better every update. A tip from me: If you zoom in from far and focus on the car, and put motion blur on 60 you'll get a great looking pic mostly. The most far you can go is 687 mm, so if you aim to at least 200mm then your pics will look more detailed and clean. But, don't get up TOO close, because then you will see bad details, like edges and bad coloring.
Well, keep it up and pay my gallery a visit too 👍