Wouldn't DD Dyemax discs be exempt from the "stolen intellectual property" argument considering that they market a service at a flat fee? They market a blank disc that they can add a logo to. Whether I purchase a disc of Superman teabagging Batman or I purchase a disc with my face on it, the charge for the product is the same. The end user submits the logo to be used and DD does not make profit directly from the advertising and marketing of the image. They are not selling the logo, per se. Where does the line get drawn? Does Warner Brothers get to go and sue all the ladies and gentlemen that received ill-advised Tweety Bird or Tazmanian Devils Tattoos in the late 80's/early 90's? What about the tattooists that did the work?
I think it eventually comes down to scale.
DC isn't going into art classes and tacking on a fee for every kid that tries to draw Batman, but if you are reproducing their exact image for a profit then you've crossed a line. Ultimately, it would probably be how far past that line you've gone and how much perceived damage/loss they think has happened to determine if they would go after you.
I'm not certain if the court would determine that the person who is asking to stamp a bunch of Batmen on some discs is ultimately responsible for ensuring the licensing, the stamper, or both.
It probably depends on an assumption of awareness of the image. So, if you are stamping Mickey Mouse for someone, you probably should have known better vs some obscure pop culture image you maybe thought was original.
However, I'd guess in the case of Gateway that the overarching pattern of behavior of helping to facilitate the infringement on a regular basis would probably come into play, too, since they are basically encouraging the behavior within their industry (which I assume is where Zam is frustrated) If a lawyer is going to go after anyone, they are going to choose the root of the problem, especially if it probably has the most money compared to a single person.
In terms of tattoos, thats an interesting topic that I don't know the answer to, but I'm guessing that its not worth the effort since each case would be an individual legal action, plus the weirdness of what do you do with the area of the body that Taz has unfortunately been applied to? Make them burn it off? (The answer for all Tazs, Marvin the Martians, etc is always YES)