StockSnap - Beautiful, free stock photos
Unsplash Wallpapers for Mac (Official) - Curated, HD desktop background photos from Unsplash.
Magdeleine - Magdeleine is a stock photos website offering thousands of royalty-free, high-quality photos for personal and commercial projects.
Irvue - (previously Unsplash Wallpaper) Gorgeous wallpapers on your Mac.
Openverse - Openverse is an Openly Licensed Images and Audio database and a growing community of photographers, illustrators, and musicians who share their work under a Creative Commons license.
Wallpaper Wizard - Wow-worthy backgrounds for Mac