Flickr currently hosts more than 75 million images that are licensed under a Creative Commons license, and a lot of them can be used even on commercial pages (depending on the exact Creative Commons license).
If you want to freshen up your homepage and want to link to some images from Flickr, you need to take some steps. You need to find out the correct URL of the photo and it must be linked back to the photo page; you must give the author proper credits and link back to the authors profile page; show that the photo is licensed under a Creative Commons license and finally include describing text on the image for people using screen readers.
After doing this several times, I got tired of it and created a small website that automates this process: ImageCodr.org. You simply pass it the URL (as seen in your browser) of the photo page and it will generate ready to use HTML code. Here is an example of the result.
A small link that you can drop on your browser’s toolbar is also available on the Get code! page, so you can simply click this when viewing an interesting photo.