This I think has been an issue for some time now (quite possibly deliberate too - Jay??)
Anyhow, try posting the images inline, using the code. Said pictures will have to be hosted elsewhere on the net though.
Photobucket is a fairly common choice. It's free to use, you have plenty of space, and it'll even resize photos for you on upload. Plus, once it's uploaded, Photobucket will even give you the correct code to cut & paste for forum use.
Jim