I gave my brother the task of tearing down the cabinet and after about an hour of demo it was a heap of blue boards on the floor. The below photo is a somewhat closeup view of the wall behind that massive blueness. There is some purple paint, teal wallpaper and upon closer inspection some very old brown wallpaper that proved to be quite intricate...I'm hoping that maybe it was the original wallpaper from the time the house was built; but who knows.
There are these egg shapes near the top and bottom of the wall and the entire background is covered in dark brown vertical lines. I don't know what the original color of the paper was, maybe it was brown, or maybe the colors have just turned brown from layers of other stuff on top. It would be very interesting to know how old this paper is and what the original sheet actually looked like. I'll have to do some research on this along the way and let you know what I dig up. In the meantime, if you have any theories of your own, I'd love to hear them.