If you have a blog or website, have you ever considered how much traffic is directed to it via image

If you have a blog or website, have you ever considered how much traffic is directed to it via image searches? My 4th leading referrer is... http://www.google.co.uk/imgres so if your site lends itself to images then you can find them with these options istockphoto.com and dreamstime.com for purchasing photos and stock.xchng for free photos.