batface - 3:02 pm on Nov 8, 2012 (gmt 0)
I would like to say it works, but it doesn't. I followed your steps and placed the expires htaccess in the image folder.
I am at the same position -
^126.96.36.199 = no alternative image
!^188.8.131.52 = always alternative image
I also purge the cache with Fiddler in case.
It is a fixed IP.