when you hit reply, scroll further down, and see "manage attachments" i think you can attach pics there.
another way is to post your pics on another website, like photobucket.
www.photobucket.com, then link it here.
register, its free.. then you can upload your pics there.
when you have uploaded your pics, you can see 3 "URL's" under the pic. they are "URL", "TAG" and "IMG". Select and copy the "IMG" html there, and just post it straight into the message area when you are replying a message.
this is how it looks, but i have taken out the "G" from the IMG at the end so it wont work.
http://img.photobucket.com/albums/v402/glee/P1050250.jpg[/IM]
below this is a tag that works, but you will just see the pic it pulls from the photobucket server and not the tag.
[IMG]http://img.photobucket.com/albums/v402/glee/P1050250.jpg