What you can print, and what will get an order refused
Your own photographs and words are fine. Logos, characters and other people's art usually are not. A plain explanation of where the line sits.
Most of what people want to print is entirely fine. The exceptions are consistent and worth knowing before you spend time on a design that cannot be made.
Yours to print
- Photographs you took
- Words you wrote, and ordinary phrases nobody owns
- Art you drew, or art you have a licence to use
- Names, including your own family name
Not yours to print
- Company logos and brand marks, including of companies you like
- Characters from films, games, comics and television
- Song lyrics and book passages, which are owned even when short
- Photographs and illustrations found through an image search
- Another artist's design, redrawn
The common misunderstandings
A few beliefs come up repeatedly and none of them are true: that it is allowed if you are not selling it, that changing it by some percentage makes it yours, that crediting the owner makes it permitted, or that a thing found on the open web is free to use. None of those change who owns the work.
Orders that clearly use somebody else's brand or character can be refused at the printing stage, which wastes your time rather than protecting it. Better to know before you design.
What to do instead
Describe the idea rather than copying the execution. A shirt about liking a particular sport, film genre or hobby can be made entirely from original words and shapes, and it will be more personal than a copied logo.
Fan art
The honest answer is that fan art of an owned character is a copy however lovingly it is drawn. Personal use is a risk people take knowingly; printing it commercially is not something to plan a business on.
Names and likenesses
A person's name and face belong to them, which matters for the two most common gift ideas: a shirt about a public figure, and a shirt with a photograph of somebody on it. Your own family photographs are yours to print. A photograph of a celebrity, or one taken by a photographer you hired, usually is not.
Where it actually gets caught
Nobody inspects a single shirt in a warehouse. What happens instead is that a print partner refuses a job, or a rights holder finds a listing. The cost is a cancelled order and wasted time rather than a dramatic legal event, which is why it is worth avoiding at the design stage rather than hoping.