People of all shapes can cosplay. I just saw a hexagon in a Hatsune Miku cosplay last week.
Anyway, glad to hear you've decided to start cosplaying. The people here are wicked helpful and love to give advice from experience, so don't feel shy about asking questions.
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Want to help create a US anime convention map?
COSPLAYS IN PROGRESS
Canterbury (Kuroshitsuji) - 30% - Kuro Gathering
Utatane Piko - default (Vocaloid) - 15% - Ohayocon
Boris (Alice in the Country of Hearts) - 3%
Armin/Jean/Levy (Shingeki no Kyojin) - 0%