Similar to yesterday's patch, I have noticed that in a check for
gnus-article-mode, we should be checking for gnus-picons-mode.

On the other hand, I'm not sure why there is a gnus-picons-mode.  Does 
it actually give us anything?

Maybe it should be a minor mode, and then the major-mode can still be
gnus-article-mode, and gnus-art.el doesn't need to know about picons,
and we may even be able to put picons in non-gnus-article-mode
buffers.

Anyway, here is my patch.  The line numbers may be off slightly
because of my previous patches.