You’re dealing with the trademarks and copyrights of the car companies, plus any photographers’ copyrights if you do recognizable work from their images without permission. To solve the photographer problem, find one or a few photographers and get permission, perhaps work out a trade, permission for a piece of art, if money’s tight. (Or take your own reference photos and/or sketch from actual cars.)

A LOT of tricky legal issues, none of which are defined by a handy formula, and which could even cross national borders and involve the laws of other countries, because the car makers and photographers could be all over.

Find a good intellectual property attorney; most will give you an initial consultation free, and frankly, a couple of hundred dollars to have them advise you further might be well worth it.

I wouldn’t use a disclaimer. It won’t protect you, and may demonstrate you know/suspect you’re infringing.

From what I have seen, artists who do one-of-a kind original paintings, sculptures, etc, fare better with depicting brand names than artists who upload that same image to a Print On Demand site and sell it as reprints, pillow covers, etc. This could be as much about attracting attention of brand owners, as much as any actual legal differences. I have seen many artists selling on Etsy who complain that using trademarked brands in their search tags of descriptions gets their work removed, even if the work itself might not be infringing. E.g. Onesie, Frozen, Disney inspired, Tiffany Blue, and a host of brands.

Fair use cases vary wildly; even courts don’t agree on what fair use is. But if you talk to a good attorney, and read up on it, you can greatly minimize your risk. One thing is sure; the internet is loaded with infringements and is not a good example of what’s legal. Also, google copyright myths, fair use myths, and trademark myths you will find a number of legal articles to kind of get an idea of what is and isn’t ok, and it’s often really different than what ‘everyone’ thinks.

Good luck. I have seen some wonderful art that does refer to brand named things but there is also a lot that is just going to be removed by DMCA takedown because it was too close to the fuzzy line of where fair use becomes infringement.

Unfortunately a lot of these cases come down to what the judge decides or which party can afford to fight it longer in court. This is why the IP attorneys don’t agree on what is “fair use”.

Trade marks are registered, but I have no idea how you would go about searching the registry to see if a particular item or image is trademarked.

BTW I do know a fine artist who paints cars. She has not been sued that I know of. But I am sure any lawyer would be unwilling to guarantee she never would even if she is doing very low risk work. http://torvafineart.com/torva.php/torvafineart/gallery

My own limited experience, not with my own art but in another context is that Trade Mark owners can try to push the boundaries of what they actually have rights too. Unlike copyright, a trademark has to be registered in each country in which it will be used, with some special cases like the EU.

In my case I came afoul of a TM that was only registered in the US. I was selling an item on Etsy that included this TM. It was a TM issue only since everything else was out of copyright. Etsy pulled my items and the TM owner refused to discuss the matter, even when I agree not to sell the items concerned in the US. Etsy won’t do anything without the TM owner’s agreement so I’m over a barrel, even though my contract with Etsy is under Irish law. In passing, Etsy appear to be in some confusion over the difference between copyright and TM, simply lumping them together as matters Intellectual Property. They are of course but the legal context is different.

I looked at registering the TM (just words) in the UK myself, (perfectly legal) but reluctantly decided against it since the income generated wasn’t enough to cover even the basic costs.

So the moral for me is to take just as much care with TM items as with copyright. Even if you are in the right you may still find yourself in difficulties. You can check online to see if a TM is still in operation which is worth doing.