Staffrooms are traditionally a bit of a blind spot in the work environment.
It's where the backbiting and plotting goes on and where teachers and others seem to be able to act inappropriately with impunity. That will change if more people like yourself are prepared to make a fuss. There should be clear rules in staffrooms around the country about what is and what isn't acceptable. The fact that you are offended by these images is a good enough reason for them to be outlawed. Perhaps if these magazines were finally to be certified as pornographic, an issue recently brought up in the House of Commons, you may have a stronger case. But as this probably will not happen it is the responsibility of colleges to look into this matter. There is also a bigger issue here. As a teacher is it enough to pay lip service to issues such as equality and social responsibility? Surely, you have to be seen to be a believer and a practitioner too.