I like the second image as well, the graphics you've added create a sense of motion and speed in the image, which really helps sell the car.
The go cart image is good but shouldn't be all blurry, the idea of these action shots is to have a very crisp focus on the subject and to blur out the rest of the shot to add to that focus. The signature on that shot distracts a bit, perhaps make it smaller or make it stand out less.
Overall nice work though, and very good for so called "amateur" pictures