Here's a tip to help you avoid double-posting:
You have a topic
It gets many replies
It gets bumped down because it is old and no one is replying
You update it with new pictures
Edit your original post with the new pictures and a thread title that says UPDATED
Post a reply. This will 'bump' it up to the top
Delete that post. Note that this can be done only until someone replies.
Now, you've got an updated, viewable thread with out any meaningless "updated!" posts.
If the admins think this will cause too many problems, feel free to delete it. I'm not trying to get people to bump all their old MOCs up unless they are updated.