A good background image can boost your productivity and even improve your mood. It can also lend a little freshness to an aging device. If you are not interested in using your own images as wallpapers, you can choose some beautiful ones for these sites:
The advantages of Desktoppr are that only high-quality wallpapers are allowed into the database and it syncs right up with Dropbox so saving an image to a computer or mobile device only takes a couple of clicks.
Wallhaven is a replacement for Wallbase.cc. It is still in the early stages of development but there is already good stuff on it. It has multiple ways in which one could search for pictures using the toolbar at the top of the screen.
DeviantArt has a number of impressive wallpapers that users can get at by clicking Customization and then Wallpaper from the front screen. It also has numerous sub-categories that can help in your search.
On Flickr there are groups dedicated to pooling wallpaper images as well as groups centered on almost every other topic you could think of. It has strong features and you can even upload up to 1TB of your own content to share.
5. Google Images
Google has a lot of nice images. Some advantages of Google are that it displays the most popular images, allows you to choose images by size, and it allows you to search for images based on a topic of your choice.