It's a drawing challenging, but if you'd like to participate with typography and such, I think it would be interesting.
Any ink is okay! You could use markers, ecoline, nankin/sumie ink, etc. You could also sketch it first with a pencil, just make sure to ink it. Check out the hashtag, you'll see a lot of examples from previous years.
I guess the only thing that isn't allowed is digital artworks and plain pencil sketches.