I've got a world map at the back of my classroom surrounded by pictures and quotes from famous mathematicians, with string showing where they came from. Pupils have added to it to include what they are famous for, and have created their own biographys for people I didn't include in the first place. I love it, and the students seem to like it also. I also created a timeline going round my room, showing key times/dates in mathematical history. A couple of pupils came to me to talk about the Rhind Papyrus as they'd read about it on my wall, and went and saw it at the British Museum during half term. The Babylonian era seems to be quite interesting to them also - my Y10s are bemused about why we talk about Pythagorean Triples when they are inscribed on a bit of clay years before hand. Its nice to talk about something different in the last few minutes of lessons.