Paint a feeling. Choose an emotion and paint it. Try anger, joy, sadness, shyness, or love. Try painting tree branches blowing in the wind. Try contour drawing.
Line drawings can surprise even the most experienced artists.
That's one reason why contour drawings are a favorite warm-up exercise. You can make a contour drawing with a pen, marker or crayon. Choose an object and begin by placing your pen on the paper. Let your eyes travel slowly along the outside edge of the object. Notice and record with your pen every bump and dip on its edge.