It could very well possibly be what you're taking the link from. Feralheart forum doesn't support Tinypic so I suggest Postimage or another like that! Hope it works out, and you get it to work! And yes it should be [ i m g ] link [ / i m g ]
For the image, make sure it has a type of format behind it [.jpg, .png, etc.] and that you close the tag with [/img]. Other than that I'm not sure what the problem could be