Monroville said:
Maybe if the mountains were more grey or a faded blue due to atmospheric haze - something to distinguish them from the ground below the AT-ATs so it doesn't look like they're right behind them.

The other day I caught an episode of the show 100 Places to See Before You Die and it was an episode about Alaska. At one point they flew a helicopter to the top of a giant glacier and while they were up there it was nothing but snow and mountains. The thing was though that the mountains looked like they were a short walking distance away but in fact were miles and miles away. The illusion was caused by the clear air and snow.