You might try adding 'foggy' sprite image, decrease it's opacity, place on a layer all across your layout, give them the 'bullet' behaviour, and set speed to something like 5-10 pixels a second. You can add as many images you like and they would slowly move across the screen.
Hard to explain but I've amended someones capx (sorry whoever you are - can't remember) to show what I mean.
Read the first posts.
That was my first idea, but it would be really hard to do 'cause as i said it is a really big room, so placing one by one the clouds would be really difficult. (Read - Take a lot of time)CenSilver2011-09-30 15:01:54