All the rewards are very focused on the product which is interesting. I don't know if this is a good thing or not. I think it is because the page is very focused on the product. But it's also limiting who will donate - maybe if we had a wider range of rewards, there would be people who donate to get the other rewards?
If you have original artwork in you book, then limited print runs of some of that art is a great idea in my mind. If they're not actually interested in the book, then bidding for unrelated rewards that happen to be attached to it seems unlikely. They could probably find those rewards elsewhere with less cost unless you find something super unique.
To answer the question - I actually like projects where all the rewards are parts of the project - as Kickstarter Only pieces especially. I feel I've gotten unique value from a unique project that will hopefully push it into going much wider in scope and availability.
My suggestions are these:
Look at your actual costs for all the aspects, printing, binding, art and what not. Those define what your goal needs to be at a minimum.
From the goal list then you proceed to the additional rewards costs - anything other than a digital item - and what it is going to cost you. Prints or art you already hold copyright to and can get made - various qualities of printing and packaging those. Is it something that can be rolled up in a tube and shipped or is it already in some kind of display format?
Kickstarters that focus on the project and offer things directly related to that project as special extras do attract attention. The thing about Kickstarter is that it can limit how you package those choices and whether people want different combinations than what you are offering. "I want two books and only three of the six prints you are offering, do you have a way I can get that?"
IndieGoGo allows additional pledges for different parts of the reward structure. With Kickstarter, you only get one pledge per account. The project creator can take on the administrative burden of keeping track of what extras folks want in addition to the main pledge - and the pledge needs to account for those costs.
Example: I pick the option of the digital and soft copy book. You allow me the option to add for prints of the art in the book and I choose two different ones. So I add what you have determined as the price for those to my pledge for the book pledge I've selected - and shipping can be a cost that will need to be made up by the pledge during survey time.
The whole making good on the myriad combinations of pledges for crowdfunding is actually a booming business for a lot of folks, with Backerkit and CrowdOx being a couple that come to mind right away. Like Kickstarter, they get a chunk of the money for handling the pledges and what not - so that cost also needs to be figured into the mix.
The digital copies, bookmarks, and printed copies are pretty standard.
Some other ideas:
-an actual mailed Thank You card from the author
-deleted scenes (things that were cut, maybe to get the page count down)
-backer's name in the acknowledgements
-if fiction, name a character in the next book
-lunch with the author (high-level reward)
-sneak peeks at upcoming work