These are thin panels, which can be fixed to the wall or ceiling. No grills at the top because they are designed to produce radiant heat ( Far Infrared) , not convected heat
Panels can be either metal fronted or glass fronted.
The metal fronted panels can be any colour, but usually white, and if required can have a picture, yours or a standard stock photo specially printed on the front, effectively meaning a picture on your wall can heat the room
Glass fronted panels can be plain, again any colour or can have a picture, either standard or your own printed on it , or can be supplied with a mirror finish.
Wireless or integrated thermostatic control is incorporated in some panels, in others an inline direct acting , wireless or internet controlled thermostats are required which are usually an extra over cost.
The range of Far infrared heaters is huge, the options for thermostatic control are also huge
Standard white aluminium panel on wall 
Standard white aluminium panel on ceiling 
Mirror glass panel on wall 
Panels with picture on wall
One thing to remember is all these panels need a power supply. So if you don’t want an unsightly cable hanging down then the cables have to be behind the wall or above the ceiling.