(It's annoying when people post in these types of threads without actually having answers, but...) I believe you can only attach pics in a
PM through a
FLKR link or the like, and not through the standard uploading of a pic in a thread post.
(Obviously, I could be wrong.)
I went to my account and copy and pasted the code for this pic in a
PM and it shows up just like it does here:
BetsyRossFlag2 by
Elms Hughes, on Flickr