A finished upstair looks much like the rest of the house. It has basic architectural elements installed over the barebones outline of the space, to enhance its appearance and convenience, such as electrical outlets etc. Unfinished upstair usually have exposed concrete facing, support beams, a lack of electrical options. You generally wouldn’t decorate an unfinished upstair.
Upstair decorating is unique because of the unique architectural obstacles you have to overcome. For example, almost all upstair suffer from a lack of natural light. Obviously this is due to the fact that most upstair are either completely, or at least mostly, recessed in the ground, which makes it difficult to install windows in their walls. And while there usually is a type of windows, these obscure openings usually have to be placed near the ceiling, and at this angle they aren’t conducive to allowing sunlight anyway, so they are more of an aesthetic feature. So, not having natural light is the obstacle that must be overcome through your choice of upstair decorating. So, when decorating, you want to ensure that there is a wealth of artificial lighting in the room.
Your choices are either: overhead fixtures, which are great because they provide the greatest illumination, but some ceilings in upstair prove to be too low for this option. Floor lamps, which may take some experimenting with to eliminate weird shadows; table lamps, which can be a fun decorating element; or another thing you can do is place mirrors opposite existing windows, because this will often multiply the amount of sunlight you can transmit through the room.
Another obstacle that is common to many upstair is the stale feeling, both in the air and through a the psychological feeling of being confined in the subterranean space. Your upstair is supposed to be a fun and enjoyable space where you can gather, play games, and spend time relaxing. This close, stagnant feeling has the potential to ruin your upstair by producing feelings of lethargy or depression, and creating health problems from the un-circulated air. Overcome this problem through upstair decorating, as well as with a good ventilation system that keeps air flowing through the space. You can also use plants in your design, or an aquarium to put a peaceful natural feel. The use of natural materials such as wood or stone can also artificially evoke the essence of the natural and make the space more pleasant.
Basically when you are decorating your upstair you want it to look and feel like a nice comfortable space. Have plenty of seating, and lots of light to make it inviting. Use repetition of some of the decorating and design elements from your upstairs to tie the space in. Try to avoid dark colors as the room will already feel darker, and should be decorated to give it a more uplifting and lighter feel. Mirrors will help make it appear lighter, and give it the feeling of more space.
Upstair decorating obstacles can be overcome with a little creativity. Use your imagination, and have fun with the space. Do not focus on the limitations, just use your design and decoration to overcome such problems. Add light to the room by installing tract lighting over artwork, or underneath cabinets etc. Do not put over-stuffed furniture in the upstairs if the ceilings are low. This will increase the feeling of being cramped, rather use items that sit lower to the ground, and are well proportioned to the room size. This will allow you to achieve the feel of more space than you actually have. However, do not leave the room too sparse of furniture or it will be uninviting.
Just have fun with it!