Outrun Ultra HD Desktop Background Wallpaper for : Widescreen & UltraWide Desktop & Laptop : Multi Display, Dual & Triple Monitor : Tablet : Smartphone
Download Triple Monitor Wallpaper
Some 48:9 triple monitor [5760x1080] wallpapers I've found work well. Seems hard to find ones that don't get grainy and are also good for gaming on middle monitor only (so not distracting).
Razer prismatic wallpapers for triple monitor setups : r/razer