Microsoft releases Beach Time PREMIUM, a new theme pack that contains 15 high-quality 4K wallpapers, the description of which reads as follows:
Imagine yourself on soft sands under sunny skies in these 15 idyllic premium 4k images. These images are free for Windows 10 Themes and are to be used as desktop wallpaper only.
After downloading the collection, go to Start > Settings > Personalization > Themes and click on the theme you prefer.
To apply and change to the most appropriate color, based on the current wallpaper, go to Customize > Colors > Automatically select a primary color from the background.
Find the new Beach Time PREMIUM in the Microsoft Store here.