[ Editorial Note: I'm sorry to post this late, but family obligations kept me in another county from my computer. ]
Wallpaper is not the most glorious subject to consider when thinking of ways to cover interior walls. It comes in third place, after starship master system display panels and linings with the substance that makes gecko fingers sticky so that you can just put things on the wall, or climb up it whenever you need to get away from something on the floor. Unfortunately with the sticky walls you'll just have that thing you're trying to escape follow you, so that makes wallpaper more practical, since you then won't have so far to fall.
The first wallpapers appeared in England and France around the time of the Hundred Years War, and as with many new inventions were designed to resemble the things they replaced. Thus for over three score or sixty years, whichever comes first, the only available patterns simply looked like the walls they were covering. The result was that a well-made, properly installed wallpaper was completely unnoticeable. This was quite satisfactory, particularly since at the time each piece of wall paper had to be made by hand, and an overworked paper-printer with a touch of deviousness could simply let a room be and claim it had been installed. But the idea of wallpaper as decorative in its own right came about when Catherine of Valois discovered the wallpaper for two rooms had been swapped, so each looked like the other, something she found delightful. Soon people all over Valois were setting their rooms to look like other rooms, and within a decade nobody was quite sure which room they were in or thought they were supposed to be in, and people would just hide under the covers until they felt sure of themselves again, and they never really did, which may be part of why you never hear from anyone from Valois anymore.
Over the 17th century wallpaper broke out of its depictions of walls and turned to showing pictures of heroic or stirring or simply attractive outdoor scenes, and after the Act of Union 1707 it became a great joke to put up wallpaper with pictures of room exits to make ordinary rooms harder to navigate. The Napoleonic Wars saw disruption of trade and tens of thousands of people killed, depressing the wallpaper industry and the survivors, and British homeowners turned to printed steam wallpaper. This fad was short-lived as the time and expense of continuously heating water up to boiling to be adhered to the walls was beyond the reach of all but but the regent George IV, and even he lost his fondness for the material the day he tripped and fell against the wall and a ten-foot-tall strip of steam-impregnated paper covered him. Later innovation discovered ways to use the steam to print on paper, and with this room-temperature wall covering people were glad to put up elaborate pictures of steam engines on their walls, particularly in the Watt, Brunel, and Stevens homes. Other people were less fond of it, but it was better than pictures of English room walls from the era of the Hundred Years War.
Modern wallpaper now comes in many regular geometric patterns, often with only tiny differences between up and down, to make installation a much more exciting and surprise-filled process. Most practical for some time will be a solid block of blue or green, suitable for use as a Chroma-Key filter, so that web camera conversations and recorded home movies can replace the background with an appropriately sweeping venue. You won't see anything in reality except for the solid green or blue, except perhaps for small temporary marks used to get eye lines correct, but the effect for people using your life as a source of entertainment will be worth it, except to you.
Trivia: English King Henry V's first parliament, meeting at the Painted Chamber at Westminster in 1413, provided him at least £10,000 for the upkeep of his ``hostel, chamber, and wardrobe.'' Source: Shakespeare's Kings, John Julius Norwich.
Currently Reading: The Invention of Clouds, Richard Hamblyn.