We have one of the largest free image database which you can use to download and license images free of charge. We also have a commercial section but these images cannot be downloaded free of charge. In order to search for free images only, please use the appropriate tab on the main menu toolbar: http://www.dreamstime.com/free-photos
Note that once you access an image detail page, you may be offered similar choices from the commercial Royalty free section on the same page. Ensure that you check only the free of charge ones.