If black and white gets a little boring, but you don't want to create something in full color - you can also create a monochromatic figure drawing. All you need is a neutral background and 3-4 pastels or pastel pencils of the same color, but different values.
Start with the lightest value and sketch the entire form - defining the major areas of light and shadow. This should take at least 10 minutes. Next, use your middle tone to further define shadows and form. This should take about 20 - 30 minutes. Reserve your darkest value for the last 10 - 15 minutes of the drawing - you should only put the darkest value in the deepest shadows. Don't over-use it.
I like working with a monochromatic palette...it can create a strong emotional content to the piece. And don't hesitate to try a bold color!