First image (from a set of 3) from portfolio of the talented - Elizabeth Meyers - featured in gallery and shared from her courtesy under free license (CC0). Big grizzly bear in this wallpaper which is optimized for fit perfectly in phones and desktop backgrounds or for use in blog articles, apps, 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)