Three signatures? I assume they are for Shinji Mikami, Naoki Katakai (Art Director), and Masato Kimura (Producer).
You should probably hang this in your Great Lord's Shrine.
It's actually just the Great Lord's signature written vertically in japanese with a golden marker which makes it all the more awesome! (You can see that the letters are the same in both signatures, just different orientation)
I'm gonna frame it and put on my wall. When the game comes out, I'll get a stand and put it behind me while playing so people can see the greatness!