#1. Why bother to photograph a dirty car? What are you trying to say?
-I'm an avid Subaru enthusiast and enjoy getting my car dirty for time to time. So, I suppose that picture is more for the Subaru fans than a real work of art 
#2. It doesn't come together. With the solar disk as the central point, consider how effective the picture would have been if the silhouetted figures appeared to be looking at it. Again, it doesn't say anything.
-I saw some strangers playing volleyball and thought it looked like an interesting subject. Didn't really plan it out, but I suppose I need to do that more!
#3. What are you trying to say? [I already know how to spell Porsche.]
-Just a cool looking shot, I thought.
#4. A few minutes spent with Gimp or Photoshop would have permitted you to straighten out the horizon. It would then have been a good picture. Learn to center the horizon while taking similar shots with short focus lenses or use post-exposure correction.
-I don't know how misaligned the horizon was, actually. It was shot with a 15mm fisheye lens, so some of the flaring of the edges is because of the lens.