Historical Stock Photos.com

http://www.historicalstockphotos.com/

Historical Stock Photos.com is an online stock photography resource where you can browse and download free stock photos of historical reference. You will find anything from war posters, portraits of famous historical people like Abraham Lincoln or Albert Einstein, to simple-life shoots of the past years.

You can browse all the stock images by using the category list on the right sidebar. To download the free images to your computer, just right-click any image with your mouse and then choose "Save As...".

Karen’s Whimsy Public Domain Images

http://karenswhimsy.com/public-domain-images/

Karen’s Whimsy Public Domain Images is a free online stock photography website where you can find free images for your website coming from a collection of old books, magazines and postcards, which are all released under the public domain.

You can browse through the categories of the site or use the internal search engine to find all the free images that you need. To download any of the free pictures, just right-click the image with your mouse and choose "Save As..." to save it to your computer.  

Free Artistic Photos

http://freeartisticphotos.com/free-pictures-fine-art-photography

Free Artistic Photos is an online stock photography resource where you can find tons of stock photos to use for your website and creative projects.

The service has been through a recent change in rules and now it allows you to download for free only the photos shot by Husac Lucian, the founder of Free Artistic Photos. The images from other photographers are also available, but they are offered for sale. All stock photos are available in high-quality and they vary from 600 pixels to 900 pixels in size.

Web Gallery of Arts

http://www.wga.hu/

Web Gallery of Arts is an online art museum which showcases a vast selection of artistic images that you can download for personal and educational purposes only. 

You can browse through the images of the museum using the internal search engine which helps you refine your search very precisely. If you want to use the images provided for any reason other than personal or educational matters, you should ask for the permission of the owner.

US Fish and Wildlife Service

http://www.fws.gov/digitalmedia

US Fish and Wildlife Service is a free online stock photography site where you can find free images (along with free video and audio clips) related to nature released under the public domain.

Most stock images on US Fish and Wildlife Service are available in JPEG or PDF file formats. The free images are in both high and low resolution and in different sizes. Use the browse link to go through the images you are looking for. Once you find what you need, just right-click the image to save it to your computer.