Howdy! I tattooed for a few years and nowadays, I sell watercolors and woodburnings from an art booth, at least once a month. I've found that stylized fan art is easier to sell than art that simply looks cool. The older the property, and the farther from the source material, the better. I suggest keeping away from the original logo. The pieces sold should very obviously not be misrepresented, by the seller, as part of a famous brand. Depending on location, there are legal protections for satire, so fan art mocking the original is (probably) legally safe as long as it isn't spreading lies about the brand indicated.
Pop art, especially of the fan variety, is this weird middle ground between making and taking. As long as there is enough spin, it can work. Aside from Andy Warhol and Banksy, there is a contemporary artist, Noah Verrier, who paints still lives of very popular fast food meals in a classical style. While his painting may feature Taco Bell brand food and the logo for instance, I highly doubt Taco Bell would have a case against him, nor that it would be in their interest to pursue one. Reminding everyone Taco Bell exists, by posting his paintings to social media and sharing them in public, is a boon to the Taco Bell brand. Free advertising, in essence.
It helps to pin down an audience too. I was a kid in the 1990's, so products and ads that are nostalgic for me, and the millennials I connect best with, aren't tracing back to the 1980's. If I'm leaning hard into nostalgia to sell art, then I can move beyond my own background and simply make what will sell. But, I won't be able to speak knowledgably about the source material with the customer, and it's possible I'll be less passionate about creating the purely commercial piece. When I tattooed, I included Kewpie dolls in multiple sheets, despite never having no relationship to that product. It wasn't until this year I learned these were originally collectible figurines, as opposed to toys.
With the winter holidays coming up, I've been making wall art that appeals to millennials, while debating pushing the content back even earlier. This month was busy and next month is busier, so I'm limited in how much I can make by then. Given the time restraints, I've been restricted to only those designs that I'm fairly confident I can sell. However, I plan to expand my inventory over time to touch on more nostalgic content, mainly of old toys. Recently, I made wood burnings of a 1990's style Troll doll, complete with the gem belly, and another of a Lisa Frank style Furby. I plan to make another Furby today, and have a growing list of other nostalgic properties worth making art about.
Without further ado, here are some old brands/toys/characters I can see appealing to millennials, a Gen X audience, or prior generations.
Pokemon
Barbie
Furby
Troll Dolls
Cabbage Patch Dolls
TY Beanie Babies
Polly Pocket
Sailor Moon
Neopets
Lisa Frank
Chia Pets
Kewpie Dolls
Precious Moments
Tamagotchi
Mr. Potato Head
My Little Pony
Bratz Dolls
Rainbow Brite
Candy Land
Raggedy Ann
Glo Worm
Care Bears
Lego
Garbage Patch Kids
Digimon
Harry Potter (Controversial. I recently witnessed someone pull their friend from my booth over a Harry Potter themed flash sheet I made back in ~2015, way before it was common knowledge that the author is transphobic. So, delve into this brand at your own risk. I won't make more once I sell what I have.)
For all of these, I suggest looking to their vintage designs, as opposed to the contemporary. The new TY Beanie Babies and Troll dolls hold zero appeal for me, as someone who grew up with those older looks. The more iconic that version of the original source, the more memorable and the easier for buyers to make the connection. And children would rather their parents buy them the actual toys, as opposed to art thereof, so children aren't generally who I market to.
Some companies are more litigious than others. It's risky to make fan art and tag it as the brand name when selling online. Mattel, for instance, trademarked a specific shade of pink for the Barbie movie. It would be unwise to use that shade of pink while selling stickers on Redbubble, especially if the product was hashtagged accordingly, as Mattel would likely take notice. Maybe Banksy can afford to fight lawsuits by major corporations regarding his interpretation of their brand in his art, but most small sellers don't have his resources. Especially when the company suing is Disney.
If you look at Dolls Kill, Loungefly, or scroll Etsy, you're bound to see products references some of these brands. And which brand referenced will rotate with the trends. Currently, I'm seeing a lot of Barbie, Furby, Care Bear, Lisa Frank, Polly Pocket, and Candy Land merchandise. Good luck capitalizing on trends! I drop a new blog post every Monday. Toodles!