I have this book, but where atm i don't know.
You could use the basketweave tip (just have the flat side out) or a rose tip like 104. The rose tip would probably be a little bit more dramatic with the one side a little thicker than the other.
I think the icing looks like it was "scored" with something rather than piped. Looks cool though!
I would try a 101 or even 101S, they're shaped like the rose tip only smaller.
I like the look of this cake - let us know how it turns out.
Thanks you guys!