The fourth source is commercial image websites. Some offer free daily images, many offer low-cost, high-quality images.
Getty Images http://www.gettyimages.ca/ is a well-known source of high quality images. You can purchase various rights to millions of quality images… and as of Feb 2014, they are allowing their images to be embedded on websites for no charge. The images are embedded through an iframe which pulls from Gettyâ€™s CDN, and are watermark free, though there is a 75 pixel-high footer included.
You will need to copy and paste the code in Text view on WordPress.
Fotolia – http://www.fotolia.com/
Great quality images at a low cost. Create an account and purchase credits to download images.
iStockPhoto – http://istockphoto.com/
A bit pricier but if you cannot find an image you want elsewhere, a great option. They are the semi-professional/amateur arm of Getty Images.
Stock.xchng – http://www.sxc.hu/
Back to free but with ads for paid images top and bottom. Over 400,000 imags. Great source of background images and patterns.