Works of art that express a fearful/anxious tone might depict characters that are ill-at-ease, frightened, or terrified. Beyond representation, art elements such as darker values with flashes of strong color, tentative/erratic paint application, and/or shaky lines might contribute to a fearful/anxious feeling.
Artists might impart a fearful/anxious tone due to their own anxiety, or artists might choose to evoke this tone as a reflection of the character(s) or scene being portrayed. A fearful/anxious tone might also be adopted to suit a piece that will be shown in a setting that demands an expression of anxiety.
Featured: The Scream by Edvard Munch.