Lol, I wish I asked for a photoshoot... damn you :P
1st shot: Her gun seems be pointed LEFT. The crop should show her on the right because o f that - to add some flow into the picture... because as it is the right side of the photo seems pointless at the moment. If you know how to manipulate using Lightroom the red should be less saturated and since you have no flash and you should add a radial filter around her face and increase the exposure since the camera focus is on her face.
2nd shot: Shots like these are best if you showed the background more. The shot seems to rightly cropped to leave an interesting picture.
3rd shot: Again, odd crop. If you're going for these shots, show all the way to the shoes. Or at least crop it off right after the a tiny bit of leg after skirt. Cutting after the knee is a very odd crop.
4th shot: Again, should more background or more of the cosplayer in these type of shots. Her arms seemed cut off since its cropped that way.
Take these with a grain of salt. Just my opinion, of course.
PS. If you have a Flickr add me! Flickr