When I first got a second monitor I looked around for quite a while to try and find a solution for stretching a wallpaper across dual monitors – Windows was repeating the first half of the wallpaper on both the monitors.
I eventually came across DisplayFusion which seemed to satisfy the bill – The free version allows you to stretch wallpapers across your monitors as well as drag maximised windows between screens (an incredibly useful feature).
I was fairly happy with using DisplayFusion to solve the problem, however it seemed odd to me that Microsoft didn’t include some kind of option in Windows to do this by default. It actually turns out they did – When you choose your wallpaper you have to set the “Position” option to “Tile”.
It’s kind of annoying seeing how simple a solution it is having spent quite a while looking for it!