"Waste paper" as it was called, was commonly used for mosaic patchwork
18th-century British wallet pieced of silk triangles
over waste paper
Two mid-19th-century hexagon patchwork tops
"A favorite night's employment was found in making envelopes. No bits of white paper suitable for writing with pen and ink could be wasted in envelopes. Thus it happened that wall paper and sheets with pictures on one side,...served to make envelopes, neat enough. These we stuck together with gum from peach trees."
These envelopes have been folded to show the wallpaper inside.
When mailed all that was visible was the back of the paper.
The Smithsonian shows a small collection of adversity covers here:
Wallpaper was also used for book publishing as in this
novel printed in Mobile in 1865.
Most famously, the Vicksburg Daily Citizen was
printed on the reverse of wallpapers during the seige of
Vicksburg in 1863.
This issue from the Library of Congress shows a sample number on the colored wallpaper. I would
guess most of these recycled wall papers are from sample books or unused rolls of paper. The idea of ripping the paper off the wall is more romantic, but sounds rather impractical.
Private letter writers, government document printers and publishers used other kinds of waste paper with blank backs, much as seamstresses paper-piecing hexagons and mosaic patchwork had been doing for decades.
William Watson's memoirs include a recollection of a special wartime paper manufactured in the Confederacy:
"Ordinary writing paper had now about disappeared, and all the army forms and documents were made of some kind of home manufactured brown paper — something like that used by grocers in wrapping up goods."
See more about adversity envelopes here:
Hexagons in a mix of styles:
Mid-19th century red and green applique with rosettes.
Unlike the scrappy tops above, this one is quilted.