3840X1080 Wallpaper 4K Msi / One site with wallpapers at high resolutions (uhd 5k, ultra hd 4k 3840x2160, full hd 1920x1080) for phones and desktop.

It has a free version that can manage wallpapers, but the full version ($30 on steam) is even better and worth its price imo, with features for customizing desktop icon profiles, windows logon.