When I was there, I was expecting the iconic god image to be huge but it was only a small part of the ceiling.

In fact, even though the ceiling takes most of the fame, my favorite painting was Michaelangelo's Last Judgement depicted in the altar wall:

http://en.wikipedia.org/wiki/The_Last_Judgment_(Michelangelo...

The later-added fig leaves and robe parts do stand out which I thought was a shame. Lots of art in the Vatican museum have private parts which have been broken (in statues) or covered/painted over.

Another impressive point that stands out is that the ceiling is mostly flat. The painted arches and columns give it an amazing 3D look.