you are not linking to a picture. you need to find the picture that you want as your image. then right click on it and click properties. it will give you the URL to the image. then you use that. however, if you are taking a pic from the gallery, use the thumbnail (small image) because if you use the actual image it will be huge and the board will look funny.
ok, so you have the link to the picture, however it's to the big one. backup in the album and get the thumbnail that you click to see the large picture. if you use a picture that is too big it messes up the layout of the board/site.
try using html code.
but you have to remove the . right before and after the < and the >