Not at all. I don't think there is any reason to restrict the kind of art or manner in which it's created. Someone could do a pencil drawing and upload a photo if they like. I hope that helps :)
Within the context of the project, ideas and characters can be revised, refined etc. So a pencil rendering of the Nanomancer for the purpose of Themis competition could become a digital piece further down the line.
Cool :)
Thanks for clarifying ☺