You can upload your picture to a service like flicker, or photobox or any other of your favourite photo sites.
Then when you go to post, theres a yellow box in the array of tools, it has a grey square in the corner, and looks like theres 2 mountians in it. When you click it you will be presented with a box, put the URL of the photo into that box, like http://www.pierce.tv/bird.jpg for example. Then it will insert it into the post
Heres one i made earlier
Pierce
Then when you go to post, theres a yellow box in the array of tools, it has a grey square in the corner, and looks like theres 2 mountians in it. When you click it you will be presented with a box, put the URL of the photo into that box, like http://www.pierce.tv/bird.jpg for example. Then it will insert it into the post
Heres one i made earlier
Pierce