It's said that there are nearly 300,000 surnames in Japan. Of course there are many uncommon ones among them, but you would need to have hundreds or maybe thousands of surnames for reference in your list. You also need to gather given names, needless to say.
Another and a more difficult problem is that hand-written signatures often look quite different from printed ones. It's often hard to read even for natives. For example, the second name from the left in the first picture is 河内政治郎. Do you think you can identify the kanji used there?