I asked the same question many months ago - the answer is that you have to put the photos on a website somewhere first. Many APers have a website or blog that they put a link to, but there are also some public domains where you can put your photos and then link them to your log.
Facebook being one of them
once you chuck them on facebook type [img src="url_of_your_photo"] but replace the [ and ] with < and > respectively...