Oh! Simple really. Here's an example of an image with "dynamic" tags. The part highlighted in green is what you would need to remove to make the image work.
Won't work
http://cdn1.knowyourmeme.com/i/000/079/217...87402819348.png?1287945507Now, if you removed that and then used the IMG tags, it'd come up as this.

So basically, whatever image you're trying to use, make sure it ends with .jpg, .png, or something similar to that, instead of random numbers.