I don't have scans of the Stick boards here, but there's really nothing special going on with them. They do use the same type of Stick as the oldest version (MSU PP) and latest version (VX6) PS3 controllers.
What is interesting is the main board here is multi-layer, the third controller I know of that uses a multi-layer board now (first was the PS3 Move, second was the 360 CG3 Halo 4 controller) and I imagine before long this will probably be the norm.
All of the buttons are Common Ground, so adding some additional Tact switches or whatever isn't too difficult.
TP10, TP20 - Battery + (3.7v - 4.2v)
TP21 - Ground
TP31 - Analog Voltage + (3.2v)
D1, D2, D3 and D4 - (Player LEDs*) 0603 Blue
* If the Player LEDs are replaced with ones that require a lower forward voltage (1.9v or so) the Resistors R19, R20, R21 and R22 may need too be changed to a little higher value. The default value is 470ohm, which should be fine for any LED really, but to keep the current draw down any 1.9v LEDs (Red for example) should have the Resistors swapped out for 680ohm ones.