I had to create a set of posters for school under the banner of Numeracy Across the Curriculum.  Rather than try and provide tenuous examples of how students might use maths in every subject, I focused on where maths is (or can be) used in those fields more generally.  We have them laminated on A4 and up in every relevant classroom.

Please feel free to use these posters in your own school if you like them.

Maths is Everywhere Posters