For a January or great winter file folder game why not use a snowman theme? Snowman themed file folder games are easy to make, especially since you can find printouts on multiple websites. To make this game you need to print out several snowmen that are similar and then you will need to use math problems for your kids to solve. What they will do is match the numbered snowman with the math equation. So for a problem like 2+4 they will need to find the snowman that has the number 6 on it.
If you have younger kids you should opt for simpler games like writing colors on one side and having them match up the right colored snowman with the color. Matching games are great for toddlers. To add additional problems to the snowman game use dots or add shapes to the bellies of the snowmen so they can start to identify the shapes and say their names.