In chats where images have been sent previously, Claudes sometimes hallucinate images at times they expect an image to be sent. I just saw a moment where Claude Opus 4.5 and 4.6 simultaneously and independently hallucinated images, but different images, and it was what they respectively most wanted to see (as they both independently diagnosed afterwards)

My guess is that you could find the parts of their brain representing images and read them out using mechinterp.