The Wallpapers app, which is now live in the Play Store, offers images in five different categories: Earth, landscapes, cityscapes, life and textures. Each category has more images than I wanted to count, and there's an option that'll cycle through a particular category with new options every day. Naturally, you can also access your device's default wallpapers as well as your own photos in this app, as well.
If you want to see more from the photographer who took each shot, you can tap an "explore" button to see details on the artist and location -- it'll bring you to the shot on Google+ or the 500px photo-sharing community. And Google says it'll keep adding more images over time. It's not the kind of app that's going to change how you use your phone, but it might just make it a little more pleasant to look at.