Been working in tandem with ngx_pagespeed to get a new site tuned, and am a bit annoyed seeing that big old F underneath the progressive heading.
Any chance that you can mimic the pagespeed functionality of ignoring images < 10KB in your scoring?
EDIT. Sorry Patrick, That came over as being far grumpier than I had intended!
Yeah, I can see about not including files < 10KB in the overall grade (but still flag them if you go look). Any chance you have a link to a test result just so I can make sure nothing else is going on? I assume there are no larger JPEG’s on the page, otherwise they should negate the < 10KB ones.
http://www.webpagetest.org/result/130605_Q8_1MHC/
(not my code lol)
The vast majority of those are over 30 KB: http://www.webpagetest.org/result/130605_Q8_1MHC/2/performance_optimization/#progressive_jpeg
It looks like it is mostly meta-data with a bunch of stuff from the Camera and Photoshop: http://www.webpagetest.org/jpeginfo/jpeginfo.php?url=http%3A%2F%2Ftest.spywebshop.nl%2Fmedia%2F360%2F7278-ip-netwerk-camera%2F360_assets%2F7278%2Fimages%2FSKU-7278-1.jpg
Oh, and for added measure, they have thumbnails embedded in the thumbnails 
Better lossless optimizations that can strip out most of the meta-data but maintain copyright (so it is safe to apply universally) is next on my list to nail down.
ok, it is now only warning for and grading JPEGs > 10KB
