Hi Bertrand, there is one forum thread that is currently serving as the makeshift gallery here: http://moi3d.com/forum/index.php?webtag=MOI&msg=68.1, you can upload your renders there, that thread could use a bump up anyway!
You can just upload an image as an attachment. If you want an image attachement to display inline in your message there are some instructions for doing that here: http://moi3d.com/forum/index.php?webtag=MOI&msg=68.118 .