I have these great flannel sheets from Garnet Hill. The design features include that they come in a variety of different colors and patterns (not all shown in picture), so there are options for any color palette. I especially like some of their newer geometric patterns. They can also be mixed and matched. In addition, they are incredibly durable. I have a duvet cover from almost ten years ago that is still in practically perfect condition with no holes or visible wear (except a pen stain that was my own fault).  The sheets are also extra deep, so they fit any mattress, which is especially useful if you’re a student moving around frequently. Finally and perhaps most importantly, they are very soft, comfortable and warm, which is really important in this cold climate, and these features don’t seem to diminish over time.