The best alternatives to Cole are Unsplash, Infinity New Tab, and Backdrops. If these 3 options don't work for you, we've listed a few more alternatives below.
Backdrops is a tiny chrome extension to change your boring new tab screen to an awesome wallpaper or quote of the day. All the wallpapers are designed by me. Extension can be used to change wallpapers, quote and quick links. More features will be up soon. Open to collaboration for adding new features, wallpapers and anything you want.