Look at the bottom of the Block when you are submitting a message and you will see a "Posting How to" at the bottom of the page.
In order to have a picture displayed, you need to link it to a Image file on whatever site you have. I use my Web Space to store the photo, then link to the picture so it shows up like it tells you in the Posting Hot to area.
LOL, when you hit the reply button to this message, the box opens up and is all white where you type, at the bottom of the gray box that surrounds it, all the way down to the left in the corner, you will see two spots to open. "Posting How-To" and "Posting Guidelines” Click on the How to and it will explain everything.