Along the lines of copyright issues.
I took the photograph below in 1986, of Paul Newman racing at Portland, Oregon.
Recently I copied the slide with my Pentax K5IIs, then worked on it some in Photoshop, and came up with something I wanted to print on a t-shirt. The first t-shirt company I tried refused, citing a recognizable image of Paul Newman. I insisted that since I own the image, it is mine to do with as I choose, no matter who it is a photo of. They still declined to print up a couple shirts for me.
So I found a different company that would do it, no questions asked.
The original image:
After some Photoshop work:
I also did something similar with a photo of me racing at Portland in my 240Z.
Not a single complaint from the same t-short company that refused to print up the Paul Newman picture, and I didn't take the photo, and only own the color print I bought from the original photographer, Mike Cole in Portland.
The original print:
After some Photoshop work: