There is disclosed an apparatus having a display zone, such as a liquid crystal screen (4), and including an optical device for forming a decorative pattern in the form of a figurative image. The optical device for forming a figurative image includes an optical guide (1), at least partially superposed onto the display zone (4) and having two large faces (10, 11) and one lateral face (12). Optical extractors (20) each having at least one surface (21) for reflecting light are arranged in a first group in at least one of the large faces (11). A light source (8, 8a, 8b, 8c, 8d) is arranged so as to emit light in the direction of the reflective surfaces (21) via the lateral face (12) of the optical guide. Thus, each of the reflective surfaces causes a reflected light beam to be formed in a well defined direction, the set of the light beams forming a figurative image in that direction, which can typically be chosen to be the normal in relation to the mid-plane of the optical guide. The optical guide according to the present invention is further provided with a second group of optical extractors having a predefined position in relation to the display zone (4), for illuminating the latter, possibly in relation to the same light source as the first group of optical extractors.