Roy Tanck has released a web service '4K Desktop wallpaper generator ' that can randomly generate 4K resolution wallpapers for free, so I will actually use it to generate wallpapers for 4K monitors.

TCL’s 57-inch 57R94 curved monitor brings dual 4K resolution in a seamless ultra-wide 32:9 display.

MSI's MAG 321CUPDF is the world's first dual-mode curved gaming monitor capable of 4K and 1080p gaming with 160Hz and 320Hz refresh rates.