I'd do something simple like a cat or dog. Cat could just be black leggings and top, make a tail and some ears on a headband. Bit of face paint. Same thing for dog but different ears and tail and maybe some brown patches stuck to the outfit - different face paint. Peacock sounds amazing.
My daughter is invited to a bd with dress code animals. She is almost 9. I think the theme is too childish. Would expect it for 3/4 year old. Anyway i am thinking of dressing her a peacock. What would you choose for yours???