Same with TV shows and movies I suppose. I think it’s a neat, less missable, alternative to things like graffitied easter eggs.
I can only think of a few examples like Judy from Cyberpunk 2077’s Ghost in the Shell and Radiohead tattoo that says
there was nothing to fear, nothing to doubt
That would definitely be easier but I don’t think by much these days. Lots of modern games allow you to customize your character with tattoos.
They could do something like the logo below if they were fans of Invasion of the Body Snatchers for example. Something that just looks neat to those who haven’t seen it.
It would be a little more present then some graffiti on a wall.