I don't do much on Pinterest, but spent a few moments trying to find a few boards to follow.
I was a high school math teacher, and so I enjoy puzzles. Some days I would start a class with a word puzzle, here is a board with lots of Wuzzles or "word puzzles"
https://www.pinterest.com/avidreaderadrea/fun-word-puzzles/I found it useful to print cheat sheets for my students to better manage what could go on those sheets. Here is a board with different pins containing different formulas.
https://www.pinterest.com/inshepblog/math-cheat-sheets/I was never too excited to spend time decorating my room at the beginning of each school year. But here is a board that contains ideas for math posters or sayings that would work well for room decor.
https://www.pinterest.com/pibel/math-classroom-posters/