I’ve been using relevant images in my blog posts since I starting blogging in 2003. I think it’s pretty much an accepted and expected practice as a way to illustrate how something works with a screenshot or create impact with a shot that helps tell the story or point from the post.
Over the years I’ve used image providers such as such a paid options like iStockphoto, shutterstock and the free stock.xchng. A few years ago I settled into finding images on Flickr that were designated as Creative Commons. These images are free to use in blog posts but should carry attribution and a link to the original.
Recently I switched to using a free service called Photo Pin. Photo Pin actually uses the Flickr API to help you find Creative Commons images just like using Flickr directly, but I find that my searches on Photo Pin turn up images faster and the interface is so much better.
When you select an image you are presented with up to nine size options, just like on Flickr, but the killer feature for me is that you also get a box with the HTML you need to use for attribution. Since WordPress now allows you to put HTML in the caption box of an image, you simply copy the code from Photo Pin and paste it into the caption and you have perfectly formatted attribution with links embedded.