Although I've not written a book about crowd funding here are some thoughts I have
1 - A pre-order of the VN
2 - hotkey remapping
3 - A version of the VN with a digital signature somewhere in the pages
4 - Optional Inclusion in a page of contributors (credits)
5 - Create a map of the surrounding lake side area; top contributors can be noted as property owners of those occasional places that are there. Include before/after credits or as separate media.
6 - Maybe attendance to a live Q&A some time past release?