An illumination system (2, 4, 6) comprising: - at least one light source (8, 10) for emitting light of a predominant wavelength (R, G, B; W; UV); and - a light-transmitting panel comprising a light-emitting window, a rear wall situated opposite said light-emitting window, and edge walls extending between the light-emitting window and the rear wall, the light-transmitting panel further comprising a light entrance window (21; 24A, 24B) for coupling at least part of the light emitted by the light source (8, 10) into the light-transmitting panel, said light being transported, in operation, through the light-transmitting panel substantially via total internal reflection between the light-emitting window and the rear wall; - the rear wall of the light-transmitting panel being provided with a two-dimensional array of recesses (22, 24), a sub-set of recesses of the two-dimensional array of recesses (22, 24) being distributed substantially regularly on the rear wall, each recess (22A, 22B, 22C, 22D) of the sub-set of recesses comprising scattering material (26, 28) for coupling out light from the light-transmitting panel through the light-emitting window, each recess (22A, 22B, 22C, 22D, 24A, 24B) in the two-dimensional array of recesses (22, 24) comprises an emission wall and a side wall arranged between the emission wall and the rear wall, part of the scattered light is emitted from the light-transmitting panel via the emission wall characterized in that the illumination system (2, 4, 6) further comprises a beam-shaping element arranged substantially parallel to the light-emitting window for generating a predefined angular distribution of the light emitted from the light-transmitting panel, wherein the beam shaping element is an array of lenticular elements further characterized in that the array of lenticular elements is an array which is complementary to the two-dimensional array of recesses (22, 24) in that the pitch of the lenticular elements is chosen to be such that all light emitted from a single recess is captured by a single lenticular element. - at least one light source (8, 10) for emitting light of a predominant wavelength (R, G, B; W; UV); and - a light-transmitting panel comprising a light-emitting window, a rear wall situated opposite said light-emitting window, and edge walls extending between the light-emitting window and the rear wall, the light-transmitting panel further comprising a light entrance window (21; 24A, 24B) for coupling at least part of the light emitted by the light source (8, 10) into the light-transmitting panel, said light being transported, in operation, through the light-transmitting panel substantially via total internal reflection between the light-emitting window and the rear wall; - the rear wall of the light-transmitting panel being provided with a two-dimensional array of recesses (22, 24), a sub-set of recesses of the two-dimensional array of recesses (22, 24) being distributed substantially regularly on the rear wall, each recess (22A, 22B, 22C, 22D) of the sub-set of recesses comprising scattering material (26, 28) for coupling out light from the light-transmitting panel through the light-emitting window,