I heard once, one of the reasons Encyclopedia Britannica is so costly, is the images. It takes a lot of money to buy good quality images which will be used in the articles. On the other hand the free online multi-lingual Wikipedia gets all its images for free. Have you ever thought how is that possible?
Well, Wikipedia is managed by Wikimedia Foundation and one of their projects is called Commons. Commons is a repository of free images and videos licensed under the Creative Commons. Thousands of people from all over the World contribute to Commons and all these images are used in Wikipedia. They are used in other Wikimedia projects too, and even you can use it for free and commercially too. You only need to attribute the actual owner of the media. Isn’t it cool! So what are you waiting for? Visit Commons and start using as well as contributing to it.
Now, Commons is a huge repository of media files (37,248,553 when I am writing this). Imagine how difficult it would be to search an image you want there? For that all images in Commons must be kept under suitable categories. It is always good to categorize your images when uploading to Commons. And the best part is, even after the upload is complete, categories can still be added, and by anyone. This collaborative working structure in Wikimedia makes it such a big hit and success.