You still arent using the image tags right, you need the direct link to the image, not the site.
This will not work
[img]http://memeful.com/meme/dWDaZVw/Welcome-to-Hogwarts[/img]
This does
[img]http://memeful.com/meme/dWDaZVw/Welcome-to-Hogwarts.jpg[/img]