Couple of options here:
[img src="filename.jpg"] - image is on your site to be displayed on your site
[img src="http://www.location.com/filename.jpg"] -image is on your site but you want to display it to another site via the site's BBC coding.
With the above in mind if you have html access you can also apply those two templates to something such as:
<img src="location.jpg" height="10px" width="10px" alt="Cute puppies!" />
Hope this helps, any more questions let me know!