I do have a couple of art books. Two of them are from Suikogaiden, so I can look through that for any possibly relevant action scenes. I also have a Japanese Suikoden strategy guide that might have some randomly usable art in it. I MAY have one other art book, but I think it's art from the card game anyway, so that might just be retreading the same material.
Tonight I'll probably riffle through my books and see what turns up. Then yeah, e-baying additional material might be the next option.
I'm also looking through The Spriter's Resource (http://www.spriters-resource.com/playstation/suikogaiden1/
). It has all the in-game art from Suikogaiden, which should prove useful. The only annoying part there is how often Nash is in these shots. I got nothing against the guy, but I don't want the same character appearing too often on the cards, haha.