The word 모습 is a look or an appearacne that someone or something has. It can be used for something or a certain situation. The word 몸매 is shorten word of "몸의 매무새", the style of someone's body shape or body figure. Thus, it is used only for person.

몸매 just means body figure but 모습 is a comprehensive word. (figure, form, image, reflection and etc) for example, 1. I like you "the way you are". 당신의 모습 그대로가 좋아요. 2. The "image" of his visage still haunts me. 그의 얼굴 모습이 자꾸 아른거린다. 3. By the "looks" of his outfit, he is homeless. 옷 모습으로 보아, 그는 노숙자다. usually, 몸매 is usage for people. but you can also use to animal. and 모습 is usage for everything. people, stuff, animal, scenary etc.