Yes, that's exactly how I do it–adding, deleting, changing things, etc. as I go... but starting with a photo as my basic guide. For example, in this one you can see the original photo that I started with, and my "restyle"..
This one started out as a photo of a Mustang, but after I did my thing, not much Mustang was left!
The cutaway of the 18 wheeler that I mentioned was tough, because it had to be done in Illustrator, which I don't use much for illustration, oddly enough... and second, I had no photo at all... I had to make it up out of my head. All I had were some photos of individual parts like the brake assemblies, a truck engine, etc.