I see four potential options here:
- Use a reference image of the same scene to clone in a new background
- Become extremely competent in photo manipulation and piece together what little background is available into a final image
- Hire a professional to attempt #2 above
- Use blur or synthetic bokeh to remove the distracting background in the first image
For the first image you would like to remove four cars and eight people. I see two issues with trying to do that.
- That data makes up somewhere around 15% of the entire image.
- You have very little of what you do what to replace the data with available for cloning
Did you perhaps shoot the scene twice, once with these subjects in them and once without? If you have a reference image without any of the cars, then this task becomes viable. Without a reference image in the same lighting with the same scene, this task would be out of the reach of most people's image manipulation abilities.
The second image that you would like to remove flowers from a car is probably more achievable, but it still will be a challenge.
Overall these types of skills are best left to professionals with a great deal of experience. If you simply have a photo with someone blinking and you want to fix that, I would say that is within the scope of a Q&A site like this. These are both quite advanced photo manipulation techniques and I'm afraid the steps are very involved.
The option I would suggest is sending both images off to a professional and have them try to achieve this for you. I have used retouchup.com and they would likely attempt what you desire for $10USD per image. I'm not sure that they would actually do as you are asking since it seems quite involved, but it is worth trying.
Resources For DIY
If you do want to try this yourself, we have two questions that go over the basics of object removal in images:
Addition of Bokeh
After thinking about this a bit more, I have a final option that you may have not considered. If you don't have any reference image to clone with, and your skills are not at the top end of the image manipulation scale(I don't consider mine to be), you can try adding in some type of blur or simulated bokeh. This will bring the focus to the car and somewhat remove the distraction of the other cars and people. We have a previous question that details good examples of how to achieve this on your own, here: Can I achieve synthetic bokeh? . I hope you don't mind but I took your image and used onOne FocalPoint 2 to simulate bokeh on the first image. Here are the results: