I don’t use much graphic violence in my mnemonics either, except for cartoon-style violence or something like what you might see in D&D art from the 80s.
I think that she and Nelson both mention using adult-themed images in Memory Games on Netflix.
I’m meticulous about what images go into my systems, but it’s because of repetitive thoughts. I don’t want certain things floating in my head. I prefer to seed seed my brain with beneficial images, since it affects my life significantly. I assume that most other people are different, because they pick images that I would never put in my systems. I think it’s probably fine, as long as people are fine with it themselves. 