He looks like an older grey percheron to me..exactly like my black Percheron gelding as far as size, feather and mane plus his head displays the same shape of a percheron. Belgian breeds are more roman nosed. They also come in chestnut with flaxen mane and tail for that matter..I have been around Ardennis's ( a good freind had a hitch pair)and the American ones that are here are just about all bays. Ardennes bone is MUCH thicker than your guy displays. Grey is not a color the ardennes breeders here in the states go for. The leg is not also that long. Most of your european breed Belgian lines have the shorter leg bones. Its also common for Percherons to have that full feathering...
Here are some pictures and discription... http://en.wikipedia.org/wiki/Ardennes_(horse
The other thing he could be is a cross of an American Belgian and a grey percheron.. Another good freind bought what he thought was a grade Belgian colt for a team mate for his older chestnut Belgian one...turned out he turned grey because of his Grey stallion Percheron sire.