Bjrogg,
Hey bro, stoked that you started this thread! Down here in New Zealand we don't have any snakes, and I've been thinking about alternatives for a while and just landed on the idea of fish skins a couple of weeks ago too.
I have "tanned" (urine) a few fish skins before from quite a few different species with varyied results in terms of colour retention in the finished product, any fish that were red or orange while alive (some australian species from when I was working over there) seem to turn a boring white once the scales are removed. But species that were darker coloured when alive, so generally the temperate species, seemed to retain their colour quite well and seemed to have thicker skin in general. Also I found that fish with medium sized scales tend to have the coolest scale pocket pattern once the scales are removed.
Hope this helps, I will put some photos up of some fish skins I've done so you can get an idea of how varied the end product can be, I reckon it will make an awesome looking backing! (what would I know, I've only made one bow)
also does anyone have photos of bows that have been backed by fish skins?
Zach