I'd be concerned with something like that getting caught in the moving parts or as discomania says restricting the airflow around the engine.
Besides it's a landrover, it's supposed to make a noise, put the radio on.
I've taken the standard under bonnet blanket off mine and don't often have any tunes on in the car, i'm quite happy just listening to the engine clattering away, quite a soothing sound I think.
Jon.