What would be good perennials that do not grow too tall for planting in zone 5b?
there are a huge variety of plants that would fit this description. Too many to list down. So you need to narrow the choices down. You need to provide more details such has how tall should you need your plants to be, what colour, and which area (south, north, east west facing gardens).
Also, do you want flowering perennials (plant or bush) or just foliage perennials (such as ornemental grasses or hostas, to name but a few) ?