I admit, this gift guide is a bit schizophrenic, in that I'll be covering both fun presents for kids and art-related car gifts. But, in my defense, I have a two-year old kid who loves cars and a BA in Art History, so this was kind of going to happen no matter what.
Like almost everything, the web has opened up access to many artists who do custom car-related work— you're no longer limited to paintings of rusted-out Model As by barns that seems to breed at the suburban craft fairs I remember as a kid. Artistic tastes vary dramatically from person to person, so you'll probably have a better idea of what your intended giftee likes, and my guess is you can find it.
For kids stuff, the good news is shopping for car-related kid toys is almost always fun, because gearheads generally have some part of them that never grew up, and the hardest part may be not buying extra car toys for yourself. There's so many good options out there, but I'll be sticking a few go-to ideas in Kinja for you to evaluate, judge, scorn, whatever.
Art and cars go together quite well, and there's some great artists out there doing car-related work. I'll be putting some picks in the comments, but please feel free to add your own— and if you're a car-themed artist, please, now's the time to self-promote!