4K HD Wallpaper: XDA Android Developers Forum
For those who don't know this image is somehow a fan art about one of the greatest Android Forums. If you like it, can be saved free for personal use and optimized here for fit in desktop backgrounds and homescreen phones.
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 almost all tablets)
HTC, Samsung Galaxy & iPhone: 1080x1920 (compatible with many smartphones)