It's inappropriate to share non-work related images on company time.
John is at work when Bill sends him a text of a woman with enormous breasts.
John wants to show his coworker William the photo.
John waits until lunch break when both William and him are outside and shows William the photo.
John walks over to William's desk during work hours to show him the photo.
William is delighted to see the breasts, and they both laugh happily.
William likes the photo but thinks John is doing a dangerous thing and jeopardizing both of their careers and thus William is angry.