#1 I agree with FiveRings, bring the coplayers closer would show off their costume better while still seeing enough of the building behind them.
#2 I like the over-all composition. Stopping the iris down would help show the blossoms against the bright sky better. 5.6 may or may not be the setting you need to do that. You can still save the image if you know exposure and contrast settings in photoshop. I recommend going to the menu: Image, Adjustments, Shadow/Highlight. Then use Highlight sliders do bring detail to the blossoms.
#3 Tighter cropping would bring more impact. It does not seem like a cosplay photo.
#4 I like the desaturated look with subtle hues still present. I find no problem with glasses distorting from an angle. That is naturally what they do. It is a choice. Taking lenses out fromthe glass frames can be done, but it sometimes looks noticably fake. This also does not look like a cosplay photo.
#5 You low angle action shot of him jumping is very good. The ceiling has such nice texture to show off. The timeing and pose are perfect. I prefer a candid eye-line rather than looking at the camera, but either way is still a viable choice. It does look a bit over exposed.
#6 After seeing #5 this was anti-climatic for me. The low angle is dramatic, but his pose has very little life to it. Turning his head to the right or left, looking off in the distance may have been more interesting. Your location seems cool with the stome textures, but it is so over-exposed, I can't appreciate it well.