I just installed a free stock image gallery for my WordPress blog site. Its working great.

http://wordpress.org/extend/plugins/freebie-images-free-stock-images-plugin/

Its a great stuff, just install and activate from admin section. A Freebie Images section comes to right side of dashbord while writing blog. Search for images and drag and drop. I have used an image in the right side of my blog using this plugin.