It'll work...you just need to take out the spaces. ^_^;;
See, those things (brackets around the "img" and the "/img") are called image tags because when you put them around a url of an image (tagging it, if you will), the image shows up.
However, if you just write the brackets around "img," the computer would interpret it as the forum's html-like code thingy, and wouldn't make it show up, therefore defeating the purpose of trying to show you. ^_^;;
So just take out the spaces...you want this: [ img ] without the spaces at the beginning of your url (and without a space in between the tag and the url) and one of these: [ /img ], again, without the spaces, at the end.
...I hope that helped. I am teh b4k4 at explaining things...*shifty glance*