Mirrors work for checking your appearance in the morning, but also create the illusion of more light in a room when placed properly. Set mirrors on walls opposite light sources such as floor lamps in the basement, or opposite well-lit areas such as the stairwell leading down to the basement, where a door or window might let in even a small bit of natural light. Use mirrors on the backs of bookshelves and opposite hallways to create the illusion of more space in the room. If your desk faces the wall, a mirror on that wall gives a view of the room behind you, making the workspace feel less cramped.
Light, cheery colors help the basement feel more like an office and less like a cellar than, say, dark wood paneling or dark gray walls. Choose wall colors that invigorate or inspire creativity for you a bit, such as apple green or a bright orange. Outfit the office with light-colored furniture, such as a glass-topped oak desk, or a white armchair for relaxing, rather than dark furniture -- which creates a more foreboding environment.
Adequate lighting is a necessity in a basement workspace, especially if there are no windows to let natural light in. Install modern-looking, low profile swag lights in corners of the work area for added light as well as decor, or floor lamps that shed a good deal of light without being in the way. A task light over the desk area helps directly illuminate the projects at hand. Track lighting allows you to aim the light exactly where it's most needed to create a comfortable work environment.
It's the little extras that make an office space feel comfortable, taking the drabness and drudgery out of the workday. Plants around the room add a sense of decor and nature to this spot without a view of the outdoor world. An aquarium, especially one that's backlit, offers much the same effect, adding an air of tranquility, life and motion to the space. Use colorful artwork, such as posters featuring a beach scene or hot-air balloons, to give you a faux view of the outdoors as well as a splash of color. Colorful bins to hold paperwork or office supplies provide decor as well as storage space.