4K HD Wallpaper: Flames Effect
Literally hot image from the the guys behind Skitter Photo project. the image can be downloaded free under CC0 license if you like. Here's optimized for use in desktop backgrounds, homescreen phones, apps, social media, content marketing, web design projects...
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)