aaah..As mentioned, most likely e-mail.
I remember being told about the previous contests too, "The good thing with FB and Twitter is you make it public so every submission has to pass their image requirements. E-mail though... is a private submission. There were many submissions that people... wouldn't be allowed to post on Facebook or Twitter."
in that case I'm really looking forward to what people produce
I think I might design one more... for a female character this time