If you are not signed up for BuyStitchEmbroideries you should have a look at it. About every 2 weeks they send you 5-6 free designs, almost always cute ones for children . They may not have exactly what you want right now but I thinkyou will fi.nd they are worth saving for future-"just in Case" Will also addd a couple of links ofsites with free or reasonably priced cute designs.
not free but so sweet
There is a set of funny face cars at Mtldesigns. Just click on freebies and it is the first page to pull up. I have attached the links.
Agree with starlite44 that turquoise had a cute set of cars also. My computer automatically translates from french to english for me. On the right side of the page you will see Scroll a little over half to 3/4 way down the page. On the right hand side you will see archives heading. Click on June 2012 and July 2012 and it should bring up the list of car designs. There are 6 of them. Click on the title and it will take you to the picture where you can click on link to download the design.
If you are looking for something special and you can give us more details we may be able to narrow it down for you. There are several sites out there with different types and sizes of free cars.
Look on the sew forum and do a search for toy cars I am sure there was some cute ones. Also look on the Le blog de turquoise210 you may have to hunt but she did some awesome looking cars. Janet
some cute freebies here for kids,not just cars
few here,the tow truck is cute
hope this will help you