...did you figure out how to change the sky texture? I am also working on a BattleField texture and was wondering how to edit the sky
On the SkyBG file (the white-to-black gradient picture), you can replace the picture with anything you want, but it needs to be black-and-white. We're talking solid black (#00000) and solid white (#FFFFF) and the levels in-between. If there is an error, it means it's not black-and-white enough. Play with the black and white levels in photoshop.
And remember, black shows up. White does not, so if you have a stary sky, the stars need to be black and outer space needs to be white. The easiest way to do that is simply to Invert the picture.