Outcome of the cars looks ok.
Some feedback that'll help you for next time -
Best advise - never take photos with tree's or poles behind them or next to them. It make it look like you have sticks coming out of your roof, etc.
Get up and close as much as possible to the car. The main focus of any photo is the car, not the background. Photos' with plenty of background takes peoples attention away from the car itself.
I think the best image of them all is the 4th one. however still, you do have tree's coming out of the exterior side review mirror.
Have a look at some of the photo's I posted up here in the photography section.
You'll find the cars that are on their own dont really have trees or poles coming out of the roof, etc.
Group photos are a bit different as the more of 1 item you have (example - more then 1 car) grabs the attention from everything else within the photo you've taken.
Goodluck with any future photo's you take mate