How Do I Improve How I Look in Photos?
The best thing you can do to help improve what you look like in pictures is to find pictures of you and pinpoint what makes you look good and what makes you look bad. Then try to eliminate the bad from your posing and focus on including what makes you look good. You can always ask for advice from friends or family, or even fellow cosplayers!
Some general tips for improving photos of you:
How many times do you expect to wear a costume before "retiring" it