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).
5760x1080 Wallpapers - Top Free 5760x1080 Backgrounds - WallpaperAccess
517134 planet space triple screen - Rare Gallery HD Wallpapers
Dota 2, Video Games, Triple Screen Wallpapers HD / Desktop and Mobile Backgrounds
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My Hero Academia Triple Monitor Wallpaper (5760x1080) done by /u/marmar9903 : r/BokuNoHeroAcademia
Screen Triple Screen [] for your , Mobile & Tablet. Explore Triple Monitor 1280X1024. Screen , 5760X1080 High Resolution , 5760X1080, Dark Triple Monitor HD wallpaper | Pxfuel
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HD wallpaper: 5760x1080 px Simple Background skull Triple Screen Technology Linux HD Art | Wallpaper Flare
Free download Pin Triple Monitor 5760x1080 Wallpaper I Edited Together From Bits Of [5760x1200] for your Desktop, Mobile & Tablet | Explore 47+ Triple Monitor HD Wallpaper | Triple Monitor Wallpaper 1280X1024,
5760x1080 Triple Monitor Wallpapers | TMW Best Wallpapers