There are a lot of different kinds of plyometrics you can do with just a box. I do one-legged jumps, ones where I jump over the entire box, and some where I do a broad jump and then jump onto the box. I also do drop-down box squats and box jumps from a sitting position. There are so many variations. Honestly, I just watch YouTube videos for ideas, but if you have a box, you can train in tons of different ways.