http://www.googletouring.com/create.php
http://earth.google.com/userguide/v4/ug_touringplaces.html
To add an image to a Google Earth placemark, add the following to your Description box:
<img src="http://..../photo.jpg">
Then, remove the address between the "" and enter the URL for the image you wish to use.
In Google Earth, go to Tools, Options, click on the Touring tab.
Click OK.