We all like free...
LibreStock (www.librestock.com) is a good place to start and is a search engine that combines the content of 40 other free for private or business use photo library websites.
A few free stock photo libraries we like are:
- lostandtaken.com (Free Texture Stock Photos)
Of course there are many many more free stock libraries and I am sure I will update the list to include more of them one day. If you want to suggest one that is not on the list then do please leave a comment.
Usually the only limitation with images like these is that you can't re-distribute the images on another website or on items for sale. However its always a good idea to check the copyright notice to see if there are limitations or rules that must be observed when used e.g. some may require attribution on the website that the image is used on.
In general, this may be referred to as a 'creative commons' license.
If you are gathering content for your website, you may also want to consider using free stock videos.