Where do the photos go?

I'm trying to add photos to the cars I have. So when you go into thumbnail generator, it generates thumbnails for every car though I only need about 3 specific ones. Is there any way to have it do pictures of just an individual car(s) without doing everyone?

Also sometimes the photos don't work. Is there a folder that the photos are directed to?

 

A png file in the car folder with the same name as the pc file you are making a thumbnail for should work.

 

I tried that. I went ingame and the pics were white. (no pics basically). Not much different from black with a question mark. Here's one of the pics.