Hey, to all my artistically inclined friends...

I'm currently working on the second Path mini-book, Absolution, which I hope to have ready in time for con season next year. As part of this book, I want to have several different interior artists. While I'm still a ways off from that segment of things, I wanted to get started with a quick survey.

PLEASE NOTE... I'm not actually asking for any work to be done or anything. All I'm doing is posting a survey so I can get an idea of what I can/should offer to artists who might appear in the book. I'd be very grateful if you took a few minutes to answer this. Thanks!

1) How much would you charge for a black and white illustration to appear in a small print run(100-200 total, maximum) book? Would you prefer a set amount, a percentage of sales or a combination(you have a guarantee, plus a percentage if sales exceed a certain amount)?
2) How many contributor copies do you think would be fair?
3) Would either of the amounts above change if you retained all rights to the artwork(selling the original or prints), save the book publication and possible promotional use?
4) Would the size of advertisement for your website and/or personal projects play any role in your decision?
5) If the publisher operated print sales on site for your contributed pieces(i.e., prints are for sale on the web site, with money going directly to the artist's PayPal account), would you be interested in taking part?
6) Would you prefer an assigned scene or concept, or would you like freedom to choose what you drew?

Anything else you'd care to add... suggestions, further questions, etc., please feel free to add. This is still very much a work in progress, so anything helps. I'm planning on doing a second survey for the book itself down the line, as I really want to do as much homework as I can before I begin in earnest. (Right now, I'm just working on the story itself, and not so much the printed form).

Thanks in advance for taking the time to respond!