Pexels

Anyone may submit photographs to Pexels, and the site's curators will choose the finest ones to add to the site's searchable library of public domain images. You may use the search bar to find anything particular, or you can browse by categories such as hobbies, emotions, and locations.

Pexels is a great resource for web and app designers, since it has a large collection of device pictures that are perfect for showcasing interface prototypes. A few photos border on stock photo cheesiness (things that are difficult to express written out with scrabble tiles, for example), but the great majority are unique and inventive.

Pexels offers a space photography category that looks fantastic, but keep in mind that some of the photographs are from NASA, which is one of the organizations whose images should only be used in specified settings.

• Benefits: Search top photographers
• Licensing: Free use, no attribution