I always post 12 pictures per post. 12 images is the limit, and that includes smilies, so unless I'm adding any smilies in the post, I post 12. The size of the picture doesn't matter. 12 images are allowed in one post. I've learned that from experiencing the loss of posts several times.

What I usually do is type out the whole post, and then *cut* the part after 12 pics. Then I paste the rest of the post in a reply, etc.