How do i post this pic to face book?
Just use the share with "facebook" link below the picture. It will pop up page to post on your wall.
LunaPic uses MyTheme image hosting for shares on facebook, so you may notice a mytheme reference.
You can add a message (and mention LunaPic.com if you like)
Note that animated gifs will not have a preview, but they will animate when on your wall..