Sticking aluminium composite sheets to the front of my radiators

I have 2 radiators which are oddly set back into the wall, making the face of the radiator flush with the wall level (actually stick out a couple of mm, but not much). The radiators are 1100 wide and 500 high. They are both 2 panel convector rads (i think convector.. basically not electric). For a minimal more modern feel, I am considering sticking an 3mm Aluminium Composite White sheet to the front of each one (the radiators are both currently ridged). Is this a bad idea? Will it effect how good the heat is in this room by much? Is there an alternative solution? Thanks