[3ncryptabl3_lick]

My first question would be, whats the end result? Web? Print?

I would definitely start with a vector layout. To get all the line work out of the way first. Whether its strictly vector or you want some hand painted details, that's up to you.

You'll have to determine the level of detail that you want. And obviously, because there isn't a color palette, you'd also have to decided on that. I mean you can leave those up to the artists as well or take his ideas into consideration but ultimately its going to be your call.