do you want it as an attachment? if so, use the advanced reply and scroll down just below the "submit reply" button. theres another button that says "manage attachments" click there and upload the pics. it is best to resize them before you do all this....i use the "best for web" size when i save my pics.
you can also use an image hosting service and just use the web address for the pics by using the insert image button in advanced reply mode. it looks like a mountain and a sun......