Google is your friend.
But look at the following links:
Anybody can build there own simple API's. For example:
At the page that requested the picture, have the following code.(I've made it very long with unnecessary code to make it easily understandable).
//Queries to get user name, picture from mysql database
$pic_location = file_get_contents('http://jayctech.com/pics.php?id=2');
<img src="<?=$pic_location?>" />