Post a image.
Before posting images to the board you have to make sure they are on the internet and NOT! on your computer. The images HAVE! to be on the internet somewhere. If you try to post one from your computer it won't work unless you upload it first.
The web server that the image is on has to let you to do this. It's called hot linking and uses there band width, so some hosts get butt hurt about it. Some even send a diffrent image than the one you tried to post. You can see if your picture is hot link protected by testing it HERE.
If the URL is to long the board may refuse to post it. If you want to post a pic with a long URL you can have the URL redirected to a shorter one that will post by going HERE.
Easiest way to post an image is to use board code.
Find the image you want to post, right click on it and then click on "Copy image URL". Go back to the board and paste it to the message box. Then highlight the URL (Hold the right mouse down as you drag the pointer over the URL that will change highlight color of the URL) then click on the picture icon . That will put tags [img] [/img] around your picture. Then all you have to do is post and the pic will show up in your post.