You have just found that 'fragment' of original wallpaper under a piece of drywall or behind a piece of trim. Now what do you do? You can't go down to the local wallpaper store and order 120 year old wallpaper. Fortunately there are a number of artisans across the country who now reproduce limited run wallpapers. One of the most highly recommended is Carter and Co Mt Diablo Handprints. In addition to a very nice line of historic wallpapers that they resell, the also have a reproduction service. So, if you have the money, there are now resources out there to really restore that room back to original appearance.
You can check out their historic wallpapers and get information about their reproduction services here: