http://img249.imageshack.us/img249/5770/46832418zd4.png
Upon choosing the filters, the content of the page (*the thumbnails) updates dynamically. Pretty neat I must say.

Cookie's PREF value (line break):
>> ID=8164c918fdfdc2d1:TM=1232671533:
LM=1232671533:S=whzAbQaBrJ_zMJqc <<

Live Search has something similar:
http://search.live.com/images/results.aspx?q=lightning (try in IE)

What difference is there between "black and white" and "grayscale", that is not already covered by selecting between "photos", "line drawings" and "clip art"?

[Moved from "Google Image SERP Testing?" --Tony]

Just noticed this:
http://lh4.ggpht.com/_p8NxWphdg3g/SYE--lkoslI/AAAAAAAABMY/KR4R8XGm0dY/s720/googleimages.jpg

posted here:
http://picasaweb.google.com/lh/photo/3-O7zv1DAa8XFKcmbvVBug?feat=directlink

Does anyone know how to enable this?

Joe, here's a post which includes the info on how to reproduce such a cookie value as mentioned above:

http://blogoscoped.com/archive/2008-05-26-n73.html

So I tried that, it correctly sets the cookie, but there is no effect on the image search.