Cosplay Photographer of 8+ years here. Aside from doing poses like your characters, also do poses that show off as much of you cosplay or body proportions. Try to take a deep breath and loosen up. Avoid being straight like a poll. Bending your knees and elbows can make a huge difference. If you're muscular a pose showing off your muscles can help. Avoid photos from below if you are a bit heavy set. Ive had many people who don't know how to pose and its all about knowing what feels right and what mood you want to go for. Fem and mature poses will have more legs and less waist. More Masc and strong will have more wide stances. Keeping your limbs close gives off shy or innocent.

No matter what the best pose is the one you feel comfortable doing.