4K HD Wallpaper: HOT Sunflower
One of the best free CC0 photography with a Sunflower in the spotlight. From courtesy of Pamela Webb, the image can be saved free and here's optimized for use in desktop backgrounds, homescreen phones, webdesign projects, blogs, apps, social media...
Widescreen Desktop / Macbook (Retina): 2880x1800 (fits on: 2560x1600, 1920x1200, 1440x900)
High Definition HD 1080p: 1920x1080 (fits on: 1600x900, 1366x768, 1280x720)
Samsung Galaxy Tab & iPad: 2048x2048 (compatible with many tablets)
HTC, Samsung Galaxy & iPhone: 1080x1920 (compatible with many phones)