Paint the walls a neutral gray color, if you're using the basement as a photography studio. Use a white-balance gray card as a reference, and match that shade as closely as possible. This prevents the wall colors from interfering with a subject's skin tones during a photography session if you're not using a backdrop.
Set up a lighting kit against one wall of the basement away from the windows. The kit allows you to light the studio in various ways when natural sunlight isn't enough. If you can't afford a light kit, make your own by purchasing halogen lamps and taping light gels to the outside of them or using light deflectors to diffuse the lamps to your liking.
Hang a backdrop on the wall near your lighting equipment. Black is common as a backdrop in photography, but have other colors available as well so you have more options. Use adhesive strips to hold a backdrop in place if the wall doesn't lend itself to nails or screws. Backdrops with pictures or murals are useful for specific projects.
Bring furniture into the room that aids you in your work. Stools and chairs are often used as photography props. Include an out-of-the-way work desk and video equipment where an editing computer can be set up. A comfortable chair is useful when you're editing on the computer.
Place a tripod in the middle of the basement for your camera. The tripod helps you record steady video and still photos. Placing the tripod in the middle of the room gives you access to the entire space, by simply turning the camera on a swivel, so you have multiple shot options without needing to move the entire rig.
Include an easel near the windows, if you're a painter and your basement is an artist's studio. The sunlight provides light for you to paint during the day without the need for artificial lighting.
Hang acoustic tiles on the walls of the basement for audio recording purposes, if your basement is a sound studio. The tiles are covered in cloth and help prevent echoing so you get cleaner audio without distortion.