Free to use big images. This is an interesting way to increase visibility and interest in your work. I love the aerialsl around the bay area. Being familiar with a place and then being able to see it from the air is kind of fun, in a puzzle sort of way.
If you want to use a picture in a product that you intend to sell, or to promote your business or organization, please contact me for permission (USD$ 50 for a nonexclusive license). Very large versions (at least 4MP) are available upon request.