 Re: using the last name of a sports star
It's thorny. You are trying to make money off someone else's image; it could be seen as passing off, trademark infringement, and/or personality rights infringement.
If you were obvious about it, it would definitely be.
The more you take away, the less value the design has to you and your customers, and the harder it is for the person you're ripping off to prove it.
Still, player names and numbers (for example) are pretty explicit. The entire value depends on making a reference that draws a connection in the viewer's mind. So if you fail to do that, your now legally safe design becomes fairly worthless. And if your design does have value, it's because you managed to connect with someone else's intellectual property. Meaning they can sue you.
Diminishing returns means it's theoretically possible you'll reach a point where you can scrape a small amount of value without being worth the cost or effort of suing. It's not a particularly rewarding game to play, financially, ethically, or artistically.
We can't give you a definitive answer (for that you'd need to get sued and see what a judge rules, or for the next best thing consult a lawyer to guess what the judge would rule), but you're not in a good place if you're trying this.
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Ceci n'est pas une autographe.
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