Royalty Free Photos
Creative Commons and Royalty Free Photos and Graphics
Inserting a photo or graphic in your blog will improve the look of your post and when your post is shared, the photo can be displayed to Pinterest, Facebook, Google+, Scoop.it, etc.
Sites
Photopin Probably the easiest to use for bloggers
Pixabay Free and no attribution required. On Pixabay you may find and share images free of copyrights. All pictures are published under Creative Commons public domain deed CC0.
Photobucket People post public photos here for public sharing. They have over 13 billion images, and 5 million added daily.
Wylio Another easy to use site for bloggers
Custom Social Media Images
Canva - Quick, versatile, customizeable
Pablo - Quick and formatted to work with both Facebook and Twitter
More
Google Advanced Image Search, look for "usage rights"
Pond5 – The World’s Stock Media Marketplace
Yay Images – Great Images at Budget Prices
iStockphoto – Royalty Free Stock Photography
Dreamstime – Download Stock Photography and Royalty Free Images
123RF – Royalty Free Stock Photos
Bigstock – Images for Everyone
Fotalia – Royalty Free Images, Photos, Vectors and Videos
Media Bakery – Millions of Curated Stock Photos
ShutterStock – Over 20 Million Stock Photos, Illustrations, Vectors and Videos
Depositphotos – Royalty-Free Stock Photos, Illustrations and Vector Art
Stock.xchng – The Leading FREE Stock Photo Site
Flickr / Creative Commons Attribution Licence