I've checked, and it turns out that all of the novels consistently spell it as "small council", uncapitalized.
I myself was using "Small Council" just because I thought it made more sense. Someone recently moved this page from "Small council" to "Small Council".
The HBO Viewer's Guide capitalizes it: http://viewers-guide.hbo.com/game-of-thrones/season3/#!/appendix/beyond-the-houses/4/
Janos Slynt? Edit
What position did Janos Slynt have when he sat at the Council, before Tyrion sent him to the Wall? Could it be Master of Laws, given that he was Commander of the City Watch?Eljuma (talk) 16:10, May 12, 2014 (UTC)