Natalie points at Athena-Sharon and Helo (and they physically quake when you mouseover their image(s) in the Sci-Fi.com Last Supper interactive image) ... Athena-Sharon subtley points to Adama ... Tyrol stares at the edge of his knife ... Lee stares inward, looking like August Rodin's Thinking Man ... Tigh stares at Sharon/Helo ... Roslin peers over at Bill Adama ... Adama looks ahead and stares inward ... Baltar reacts with surprise at Six ... and Six stares ahead and slightly upward (as if touched by divine light?)
The conflict in the image comes from an accusatory finger on the outstretched arm of Natalie-Six pointing to Athena-Sharon and Helo. They must do something that is central to the culmination of the story. What they have that is unique is their hybrid half-human, half-Cylon child Hera. They must make a choice concerning Hera which divides the factions and angers Natalie-Six.
Caprica Six's middle finger in her left hand seems to point toward the viewer (heh heh, a message?)