Do not choose a dark color for the walls of your basement bedroom as you have very limited sunlight in the area. You should use artificial lights in the area to make it a brighter and welcoming bedroom instead of a dark den.
You can hang a nice painting or decorative items in the bedroom to make the room livelier. Use thin fabric curtains to get sufficient light during the sunlight without interrupting the privacy of the person staying in it. You can convert it into a guest room or a bedroom for the family member who love to spend time in a peaceful atmosphere reading books or listening music.
You can use your creativity to design the bedroom or collect some unique ideas from the internet. A bedroom is a place which should be comfortable and welcoming so choose the ideas while keeping it in the mind. If your kids are going to use this basement bedroom take their help while designing their room. Chose brighter colors and make special arrangements for storage options.