We always recommend mounting the panels on the ceiling if possible. When mounted on the ceiling, the heaters disappear from view, the walls are not covered with panels, and when mounted on the ceiling, the heat is distributed very evenly throughout the room, reaches the floor first and increases its temperature in a pleasant way. When installing panels on the ceiling, try to arrange them as evenly as possible so that they look nice and symmetrical on the ceiling. If there is only one heater intended for a certain room, we of course first mount the lamp in the middle and, in the second step, mount the heater slightly to the left or right of the lamp.
However, if we decide to install the panels on the walls, it is best to place them about 2/3 of the wall height above the floor, ideally opposite the coldest wall (usually the outside wall). If there is no such option, then of course on any other wall. It is good that the panels are mounted as centrally on the wall as possible to allow even heat distribution.