There's nothing wrong with that

Just use the little tree symbol and paste that link/info into the box that comes up, or put IMG tags at the front and end of the link
So it looks like this:
[ IMG ]http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs277.snc4/40186_421784529645_729324645_5087011_3705662_n.jpg[ /IMG ]
(only without the spaces inside the square brackets)