Trading Paints adds custom car liveries to iRacing. Design your own cars or race with pre-made paint schemes shared from the community of painters.
I'm kind of a hack... I never really learned how to paint on a computer, and I'm still largely using a free copy of Paint Shop Pro 7 I got decades ago because it's the one I know most about. I like to paint cars with fictional funny sponsors. I tend to leave contingency stickers off the fake cars because most of my paint schemes are cartoonish. I forget why I prefer to use number 67, just something I've done for a while. My favorite cars are the asphalt modifieds, and when I find the time I like to recreate as many real schemes as I can, mostly focusing on series in the northeast. When I upload a real paint scheme I'll upload both the custom number version and a sim stamped version so you can pick both and the scheme can be seen by pro users and standard users alike.