Relief of Shapur II
Once, there was a relief of a seated king Shapur II (r.309-379) and several courtiers. It could be seen between the relief of Hormizd II and Achaemenid tomb II, but because it has always been exposed to the wind (unlike the other Sasanian reliefs, which were protected by sand), it is very damaged. However, you can still discern the Sasanian king, seated and seen frontally, and one or two figures to his right (if you cannot recognize it, look here). The composition must have resembled the sixth relief of Bishapur.
Louis Vanden Berghe, Reliefs rupestres de l' Iran ancien (1983 Brussels), #77.