The ephemeral nature of paper means that its not often associated with salvage and reuse. Over the years we have found many sources / instances of paper that when imaginatively considered can be a cheap decorative solution.
We’ve bought reams of misprinted handmade paper from letterpress printers, excess stock from matchbox factories, clerks' ledgers and music sheets. Generally speaking they can be treated with the same approach as any normal wallpaper.
Have fun in the smallest room with whatever archival material you come across.