If you put the direct link to an image between [img] [/ img] tags (without the space) then the image will load on the page. Instead of having lots of large images load, if people post links then they can just be cloicked on to view the image.
So:
Do post a link like : http://img525.imageshack.us/img525/3969/ballad6.jpg
Do not put the link in [img] tags.
If you have not previously released the skin then it will be vaild as long as you convert the design for the other cars.