Number 5, like in the first wallpapers, seems best to me. Good looking, while still enough negligee to look like a special hairstyle, and military enough without being bland as the shaved one. It also has, at least to me, the most "character".
I have to say I really like the first wallpaper! Maybe change the pants to something more akin to a uniform, or pilot's suit (and, er, hide the panties; nothing against them, just don't fit the military theme), and some minor details, like more Blue Planet military regalia. I like the tank-top, though. Maybe add some texture or textile "wings" to it, like it's military issue underwear.