The problem with external galleries is that eventually they will start blocking access to their photos from HuntinNet Forum.
This is exactly what happened with imagestation.com.
The best option is to follow the instructions below:
try posting a photo in Forum gallery here and linking that photo to a post.
Right below the photo in gallery you will find a complete link which you can use to put between tags.
to give you an example the whole thing would look like this:
some text
Code:
and the result is this: